/*
 * Linux Socket Filter - Kernel level socket filtering
 *
 * Based on the design of the Berkeley Packet Filter. The new
 * internal format has been designed by PLUMgrid:
 *
 *      Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
 *
 * Authors:
 *
 *      Jay Schulist <jschlst@samba.org>
 *      Alexei Starovoitov <ast@plumgrid.com>
 *      Daniel Borkmann <dborkman@redhat.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * Andi Kleen - Fix a few bad bugs and races.
 * Kris Katterjohn - Added many additional checks in bpf_check_classic()
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <linux/gfp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/netlink.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>
#include <linux/filter.h>
#include <linux/ratelimit.h>
#include <linux/seccomp.h>
#include <linux/if_vlan.h>
#include <linux/bpf.h>

/**
 *      sk_filter - run a packet through a socket filter
 *      @sk: sock associated with &sk_buff
 *      @skb: buffer to filter
 *
 * Run the filter code and then cut skb->data to correct size returned by
 * SK_RUN_FILTER. If pkt_len is 0 we toss packet. If skb->len is smaller
 * than pkt_len we keep whole skb->data. This is the socket level
 * wrapper to SK_RUN_FILTER. It returns 0 if the packet should
 * be accepted or -EPERM if the packet should be tossed.
 *
 */
int sk_filter(struct sock *sk, struct sk_buff *skb)
{
        int err;
        struct sk_filter *filter;

        /*
         * If the skb was allocated from pfmemalloc reserves, only
         * allow SOCK_MEMALLOC sockets to use it as this socket is
         * helping free memory
         */
        if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
                return -ENOMEM;

        err = security_sock_rcv_skb(sk, skb);
        if (err)
                return err;

        rcu_read_lock();
        filter = rcu_dereference(sk->sk_filter);
        if (filter) {
                unsigned int pkt_len = SK_RUN_FILTER(filter, skb);

                err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
        }
        rcu_read_unlock();

        return err;
}
EXPORT_SYMBOL(sk_filter);

static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
        return skb_get_poff((struct sk_buff *)(unsigned long) ctx);
}

static u64 __skb_get_nlattr(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
        struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
        struct nlattr *nla;

        if (skb_is_nonlinear(skb))
                return 0;

        if (skb->len < sizeof(struct nlattr))
                return 0;

        if (a > skb->len - sizeof(struct nlattr))
                return 0;

        nla = nla_find((struct nlattr *) &skb->data[a], skb->len - a, x);
        if (nla)
                return (void *) nla - (void *) skb->data;

        return 0;
}

static u64 __skb_get_nlattr_nest(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
        struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
        struct nlattr *nla;

        if (skb_is_nonlinear(skb))
                return 0;

        if (skb->len < sizeof(struct nlattr))
                return 0;

        if (a > skb->len - sizeof(struct nlattr))
                return 0;

        nla = (struct nlattr *) &skb->data[a];
        if (nla->nla_len > skb->len - a)
                return 0;

        nla = nla_find_nested(nla, x);
        if (nla)
                return (void *) nla - (void *) skb->data;

        return 0;
}

static u64 __get_raw_cpu_id(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
        return raw_smp_processor_id();
}

/* note that this only generates 32-bit random numbers */
static u64 __get_random_u32(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
        return prandom_u32();
}

static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
                              struct bpf_insn *insn_buf)
{
        struct bpf_insn *insn = insn_buf;

        switch (skb_field) {
        case SKF_AD_MARK:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);

                *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
                                      offsetof(struct sk_buff, mark));
                break;

        case SKF_AD_PKTTYPE:
                *insn++ = BPF_LDX_MEM(BPF_B, dst_reg, src_reg, PKT_TYPE_OFFSET());
                *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
                *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 5);
#endif
                break;

        case SKF_AD_QUEUE:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);

                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, queue_mapping));
                break;

        case SKF_AD_VLAN_TAG:
        case SKF_AD_VLAN_TAG_PRESENT:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
                BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);

                /* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */
                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, vlan_tci));
                if (skb_field == SKF_AD_VLAN_TAG) {
                        *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,
                                                ~VLAN_TAG_PRESENT);
                } else {
                        /* dst_reg >>= 12 */
                        *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);
                        /* dst_reg &= 1 */
                        *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
                }
                break;
        }

        return insn - insn_buf;
}

static bool convert_bpf_extensions(struct sock_filter *fp,
                                   struct bpf_insn **insnp)
{
        struct bpf_insn *insn = *insnp;
        u32 cnt;

        switch (fp->k) {
        case SKF_AD_OFF + SKF_AD_PROTOCOL:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);

                /* A = *(u16 *) (CTX + offsetof(protocol)) */
                *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
                                      offsetof(struct sk_buff, protocol));
                /* A = ntohs(A) [emitting a nop or swap16] */
                *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
                break;

        case SKF_AD_OFF + SKF_AD_PKTTYPE:
                cnt = convert_skb_access(SKF_AD_PKTTYPE, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_IFINDEX:
        case SKF_AD_OFF + SKF_AD_HATYPE:
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
                BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);
                BUILD_BUG_ON(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)) < 0);

                *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
                                      BPF_REG_TMP, BPF_REG_CTX,
                                      offsetof(struct sk_buff, dev));
                /* if (tmp != 0) goto pc + 1 */
                *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);
                *insn++ = BPF_EXIT_INSN();
                if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX)
                        *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_TMP,
                                            offsetof(struct net_device, ifindex));
                else
                        *insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_TMP,
                                            offsetof(struct net_device, type));
                break;

        case SKF_AD_OFF + SKF_AD_MARK:
                cnt = convert_skb_access(SKF_AD_MARK, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_RXHASH:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);

                *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
                                    offsetof(struct sk_buff, hash));
                break;

        case SKF_AD_OFF + SKF_AD_QUEUE:
                cnt = convert_skb_access(SKF_AD_QUEUE, BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TAG:
                cnt = convert_skb_access(SKF_AD_VLAN_TAG,
                                         BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
                cnt = convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
                                         BPF_REG_A, BPF_REG_CTX, insn);
                insn += cnt - 1;
                break;

        case SKF_AD_OFF + SKF_AD_VLAN_TPID:
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);

                /* A = *(u16 *) (CTX + offsetof(vlan_proto)) */
                *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
                                      offsetof(struct sk_buff, vlan_proto));
                /* A = ntohs(A) [emitting a nop or swap16] */
                *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
                break;

        case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
        case SKF_AD_OFF + SKF_AD_NLATTR:
        case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
        case SKF_AD_OFF + SKF_AD_CPU:
        case SKF_AD_OFF + SKF_AD_RANDOM:
                /* arg1 = CTX */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
                /* arg2 = A */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_A);
                /* arg3 = X */
                *insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_X);
                /* Emit call(arg1=CTX, arg2=A, arg3=X) */
                switch (fp->k) {
                case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
                        *insn = BPF_EMIT_CALL(__skb_get_pay_offset);
                        break;
                case SKF_AD_OFF + SKF_AD_NLATTR:
                        *insn = BPF_EMIT_CALL(__skb_get_nlattr);
                        break;
                case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
                        *insn = BPF_EMIT_CALL(__skb_get_nlattr_nest);
                        break;
                case SKF_AD_OFF + SKF_AD_CPU:
                        *insn = BPF_EMIT_CALL(__get_raw_cpu_id);
                        break;
                case SKF_AD_OFF + SKF_AD_RANDOM:
                        *insn = BPF_EMIT_CALL(__get_random_u32);
                        break;
                }
                break;

        case SKF_AD_OFF + SKF_AD_ALU_XOR_X:
                /* A ^= X */
                *insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);
                break;

        default:
                /* This is just a dummy call to avoid letting the compiler
                 * evict __bpf_call_base() as an optimization. Placed here
                 * where no-one bothers.
                 */
                BUG_ON(__bpf_call_base(0, 0, 0, 0, 0) != 0);
                return false;
        }

        *insnp = insn;
        return true;
}

/**
 *      bpf_convert_filter - convert filter program
 *      @prog: the user passed filter program
 *      @len: the length of the user passed filter program
 *      @new_prog: buffer where converted program will be stored
 *      @new_len: pointer to store length of converted program
 *
 * Remap 'sock_filter' style BPF instruction set to 'sock_filter_ext' style.
 * Conversion workflow:
 *
 * 1) First pass for calculating the new program length:
 *   bpf_convert_filter(old_prog, old_len, NULL, &new_len)
 *
 * 2) 2nd pass to remap in two passes: 1st pass finds new
 *    jump offsets, 2nd pass remapping:
 *   new_prog = kmalloc(sizeof(struct bpf_insn) * new_len);
 *   bpf_convert_filter(old_prog, old_len, new_prog, &new_len);
 *
 * User BPF's register A is mapped to our BPF register 6, user BPF
 * register X is mapped to BPF register 7; frame pointer is always
 * register 10; Context 'void *ctx' is stored in register 1, that is,
 * for socket filters: ctx == 'struct sk_buff *', for seccomp:
 * ctx == 'struct seccomp_data *'.
 */
int bpf_convert_filter(struct sock_filter *prog, int len,
                       struct bpf_insn *new_prog, int *new_len)
{
        int new_flen = 0, pass = 0, target, i;
        struct bpf_insn *new_insn;
        struct sock_filter *fp;
        int *addrs = NULL;
        u8 bpf_src;

        BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);
        BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);

        if (len <= 0 || len > BPF_MAXINSNS)
                return -EINVAL;

        if (new_prog) {
                addrs = kcalloc(len, sizeof(*addrs), GFP_KERNEL);
                if (!addrs)
                        return -ENOMEM;
        }

do_pass:
        new_insn = new_prog;
        fp = prog;

        if (new_insn)
                *new_insn = BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1);
        new_insn++;

        for (i = 0; i < len; fp++, i++) {
                struct bpf_insn tmp_insns[6] = { };
                struct bpf_insn *insn = tmp_insns;

                if (addrs)
                        addrs[i] = new_insn - new_prog;

                switch (fp->code) {
                /* All arithmetic insns and skb loads map as-is. */
                case BPF_ALU | BPF_ADD | BPF_X:
                case BPF_ALU | BPF_ADD | BPF_K:
                case BPF_ALU | BPF_SUB | BPF_X:
                case BPF_ALU | BPF_SUB | BPF_K:
                case BPF_ALU | BPF_AND | BPF_X:
                case BPF_ALU | BPF_AND | BPF_K:
                case BPF_ALU | BPF_OR | BPF_X:
                case BPF_ALU | BPF_OR | BPF_K:
                case BPF_ALU | BPF_LSH | BPF_X:
                case BPF_ALU | BPF_LSH | BPF_K:
                case BPF_ALU | BPF_RSH | BPF_X:
                case BPF_ALU | BPF_RSH | BPF_K:
                case BPF_ALU | BPF_XOR | BPF_X:
                case BPF_ALU | BPF_XOR | BPF_K:
                case BPF_ALU | BPF_MUL | BPF_X:
                case BPF_ALU | BPF_MUL | BPF_K:
                case BPF_ALU | BPF_DIV | BPF_X:
                case BPF_ALU | BPF_DIV | BPF_K:
                case BPF_ALU | BPF_MOD | BPF_X:
                case BPF_ALU | BPF_MOD | BPF_K:
                case BPF_ALU | BPF_NEG:
                case BPF_LD | BPF_ABS | BPF_W:
                case BPF_LD | BPF_ABS | BPF_H:
                case BPF_LD | BPF_ABS | BPF_B:
                case BPF_LD | BPF_IND | BPF_W:
                case BPF_LD | BPF_IND | BPF_H:
                case BPF_LD | BPF_IND | BPF_B:
                        /* Check for overloaded BPF extension and
                         * directly convert it if found, otherwise
                         * just move on with mapping.
                         */
                        if (BPF_CLASS(fp->code) == BPF_LD &&
                            BPF_MODE(fp->code) == BPF_ABS &&
                            convert_bpf_extensions(fp, &insn))
                                break;

                        *insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
                        break;

                /* Jump transformation cannot use BPF block macros
                 * everywhere as offset calculation and target updates
                 * require a bit more work than the rest, i.e. jump
                 * opcodes map as-is, but offsets need adjustment.
                 */

#define BPF_EMIT_JMP                                                    \
        do {                                                            \
                if (target >= len || target < 0)                        \
                        goto err;                                       \
                insn->off = addrs ? addrs[target] - addrs[i] - 1 : 0;   \
                /* Adjust pc relative offset for 2nd or 3rd insn. */    \
                insn->off -= insn - tmp_insns;                          \
        } while (0)

                case BPF_JMP | BPF_JA:
                        target = i + fp->k + 1;
                        insn->code = fp->code;
                        BPF_EMIT_JMP;
                        break;

                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                        if (BPF_SRC(fp->code) == BPF_K && (int) fp->k < 0) {
                                /* BPF immediates are signed, zero extend
                                 * immediate into tmp register and use it
                                 * in compare insn.
                                 */
                                *insn++ = BPF_MOV32_IMM(BPF_REG_TMP, fp->k);

                                insn->dst_reg = BPF_REG_A;
                                insn->src_reg = BPF_REG_TMP;
                                bpf_src = BPF_X;
                        } else {
                                insn->dst_reg = BPF_REG_A;
                                insn->src_reg = BPF_REG_X;
                                insn->imm = fp->k;
                                bpf_src = BPF_SRC(fp->code);
                        }

                        /* Common case where 'jump_false' is next insn. */
                        if (fp->jf == 0) {
                                insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
                                target = i + fp->jt + 1;
                                BPF_EMIT_JMP;
                                break;
                        }

                        /* Convert JEQ into JNE when 'jump_true' is next insn. */
                        if (fp->jt == 0 && BPF_OP(fp->code) == BPF_JEQ) {
                                insn->code = BPF_JMP | BPF_JNE | bpf_src;
                                target = i + fp->jf + 1;
                                BPF_EMIT_JMP;
                                break;
                        }

                        /* Other jumps are mapped into two insns: Jxx and JA. */
                        target = i + fp->jt + 1;
                        insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
                        BPF_EMIT_JMP;
                        insn++;

                        insn->code = BPF_JMP | BPF_JA;
                        target = i + fp->jf + 1;
                        BPF_EMIT_JMP;
                        break;

                /* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */
                case BPF_LDX | BPF_MSH | BPF_B:
                        /* tmp = A */
                        *insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_A);
                        /* A = BPF_R0 = *(u8 *) (skb->data + K) */
                        *insn++ = BPF_LD_ABS(BPF_B, fp->k);
                        /* A &= 0xf */
                        *insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 0xf);
                        /* A <<= 2 */
                        *insn++ = BPF_ALU32_IMM(BPF_LSH, BPF_REG_A, 2);
                        /* X = A */
                        *insn++ = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
                        /* A = tmp */
                        *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP);
                        break;

                /* RET_K, RET_A are remaped into 2 insns. */
                case BPF_RET | BPF_A:
                case BPF_RET | BPF_K:
                        *insn++ = BPF_MOV32_RAW(BPF_RVAL(fp->code) == BPF_K ?
                                                BPF_K : BPF_X, BPF_REG_0,
                                                BPF_REG_A, fp->k);
                        *insn = BPF_EXIT_INSN();
                        break;

                /* Store to stack. */
                case BPF_ST:
                case BPF_STX:
                        *insn = BPF_STX_MEM(BPF_W, BPF_REG_FP, BPF_CLASS(fp->code) ==
                                            BPF_ST ? BPF_REG_A : BPF_REG_X,
                                            -(BPF_MEMWORDS - fp->k) * 4);
                        break;

                /* Load from stack. */
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                        *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD  ?
                                            BPF_REG_A : BPF_REG_X, BPF_REG_FP,
                                            -(BPF_MEMWORDS - fp->k) * 4);
                        break;

                /* A = K or X = K */
                case BPF_LD | BPF_IMM:
                case BPF_LDX | BPF_IMM:
                        *insn = BPF_MOV32_IMM(BPF_CLASS(fp->code) == BPF_LD ?
                                              BPF_REG_A : BPF_REG_X, fp->k);
                        break;

                /* X = A */
                case BPF_MISC | BPF_TAX:
                        *insn = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
                        break;

                /* A = X */
                case BPF_MISC | BPF_TXA:
                        *insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_X);
                        break;

                /* A = skb->len or X = skb->len */
                case BPF_LD | BPF_W | BPF_LEN:
                case BPF_LDX | BPF_W | BPF_LEN:
                        *insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
                                            BPF_REG_A : BPF_REG_X, BPF_REG_CTX,
                                            offsetof(struct sk_buff, len));
                        break;

                /* Access seccomp_data fields. */
                case BPF_LDX | BPF_ABS | BPF_W:
                        /* A = *(u32 *) (ctx + K) */
                        *insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX, fp->k);
                        break;

                /* Unknown instruction. */
                default:
                        goto err;
                }

                insn++;
                if (new_prog)
                        memcpy(new_insn, tmp_insns,
                               sizeof(*insn) * (insn - tmp_insns));
                new_insn += insn - tmp_insns;
        }

        if (!new_prog) {
                /* Only calculating new length. */
                *new_len = new_insn - new_prog;
                return 0;
        }

        pass++;
        if (new_flen != new_insn - new_prog) {
                new_flen = new_insn - new_prog;
                if (pass > 2)
                        goto err;
                goto do_pass;
        }

        kfree(addrs);
        BUG_ON(*new_len != new_flen);
        return 0;
err:
        kfree(addrs);
        return -EINVAL;
}

/* Security:
 *
 * As we dont want to clear mem[] array for each packet going through
 * __bpf_prog_run(), we check that filter loaded by user never try to read
 * a cell if not previously written, and we check all branches to be sure
 * a malicious user doesn't try to abuse us.
 */
static int check_load_and_stores(const struct sock_filter *filter, int flen)
{
        u16 *masks, memvalid = 0; /* One bit per cell, 16 cells */
        int pc, ret = 0;

        BUILD_BUG_ON(BPF_MEMWORDS > 16);

        masks = kmalloc_array(flen, sizeof(*masks), GFP_KERNEL);
        if (!masks)
                return -ENOMEM;

        memset(masks, 0xff, flen * sizeof(*masks));

        for (pc = 0; pc < flen; pc++) {
                memvalid &= masks[pc];

                switch (filter[pc].code) {
                case BPF_ST:
                case BPF_STX:
                        memvalid |= (1 << filter[pc].k);
                        break;
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                        if (!(memvalid & (1 << filter[pc].k))) {
                                ret = -EINVAL;
                                goto error;
                        }
                        break;
                case BPF_JMP | BPF_JA:
                        /* A jump must set masks on target */
                        masks[pc + 1 + filter[pc].k] &= memvalid;
                        memvalid = ~0;
                        break;
                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                        /* A jump must set masks on targets */
                        masks[pc + 1 + filter[pc].jt] &= memvalid;
                        masks[pc + 1 + filter[pc].jf] &= memvalid;
                        memvalid = ~0;
                        break;
                }
        }
error:
        kfree(masks);
        return ret;
}

static bool chk_code_allowed(u16 code_to_probe)
{
        static const bool codes[] = {
                /* 32 bit ALU operations */
                [BPF_ALU | BPF_ADD | BPF_K] = true,
                [BPF_ALU | BPF_ADD | BPF_X] = true,
                [BPF_ALU | BPF_SUB | BPF_K] = true,
                [BPF_ALU | BPF_SUB | BPF_X] = true,
                [BPF_ALU | BPF_MUL | BPF_K] = true,
                [BPF_ALU | BPF_MUL | BPF_X] = true,
                [BPF_ALU | BPF_DIV | BPF_K] = true,
                [BPF_ALU | BPF_DIV | BPF_X] = true,
                [BPF_ALU | BPF_MOD | BPF_K] = true,
                [BPF_ALU | BPF_MOD | BPF_X] = true,
                [BPF_ALU | BPF_AND | BPF_K] = true,
                [BPF_ALU | BPF_AND | BPF_X] = true,
                [BPF_ALU | BPF_OR | BPF_K] = true,
                [BPF_ALU | BPF_OR | BPF_X] = true,
                [BPF_ALU | BPF_XOR | BPF_K] = true,
                [BPF_ALU | BPF_XOR | BPF_X] = true,
                [BPF_ALU | BPF_LSH | BPF_K] = true,
                [BPF_ALU | BPF_LSH | BPF_X] = true,
                [BPF_ALU | BPF_RSH | BPF_K] = true,
                [BPF_ALU | BPF_RSH | BPF_X] = true,
                [BPF_ALU | BPF_NEG] = true,
                /* Load instructions */
                [BPF_LD | BPF_W | BPF_ABS] = true,
                [BPF_LD | BPF_H | BPF_ABS] = true,
                [BPF_LD | BPF_B | BPF_ABS] = true,
                [BPF_LD | BPF_W | BPF_LEN] = true,
                [BPF_LD | BPF_W | BPF_IND] = true,
                [BPF_LD | BPF_H | BPF_IND] = true,
                [BPF_LD | BPF_B | BPF_IND] = true,
                [BPF_LD | BPF_IMM] = true,
                [BPF_LD | BPF_MEM] = true,
                [BPF_LDX | BPF_W | BPF_LEN] = true,
                [BPF_LDX | BPF_B | BPF_MSH] = true,
                [BPF_LDX | BPF_IMM] = true,
                [BPF_LDX | BPF_MEM] = true,
                /* Store instructions */
                [BPF_ST] = true,
                [BPF_STX] = true,
                /* Misc instructions */
                [BPF_MISC | BPF_TAX] = true,
                [BPF_MISC | BPF_TXA] = true,
                /* Return instructions */
                [BPF_RET | BPF_K] = true,
                [BPF_RET | BPF_A] = true,
                /* Jump instructions */
                [BPF_JMP | BPF_JA] = true,
                [BPF_JMP | BPF_JEQ | BPF_K] = true,
                [BPF_JMP | BPF_JEQ | BPF_X] = true,
                [BPF_JMP | BPF_JGE | BPF_K] = true,
                [BPF_JMP | BPF_JGE | BPF_X] = true,
                [BPF_JMP | BPF_JGT | BPF_K] = true,
                [BPF_JMP | BPF_JGT | BPF_X] = true,
                [BPF_JMP | BPF_JSET | BPF_K] = true,
                [BPF_JMP | BPF_JSET | BPF_X] = true,
        };

        if (code_to_probe >= ARRAY_SIZE(codes))
                return false;

        return codes[code_to_probe];
}

/**
 *      bpf_check_classic - verify socket filter code
 *      @filter: filter to verify
 *      @flen: length of filter
 *
 * Check the user's filter code. If we let some ugly
 * filter code slip through kaboom! The filter must contain
 * no references or jumps that are out of range, no illegal
 * instructions, and must end with a RET instruction.
 *
 * All jumps are forward as they are not signed.
 *
 * Returns 0 if the rule set is legal or -EINVAL if not.
 */
int bpf_check_classic(const struct sock_filter *filter, unsigned int flen)
{
        bool anc_found;
        int pc;

        if (flen == 0 || flen > BPF_MAXINSNS)
                return -EINVAL;

        /* Check the filter code now */
        for (pc = 0; pc < flen; pc++) {
                const struct sock_filter *ftest = &filter[pc];

                /* May we actually operate on this code? */
                if (!chk_code_allowed(ftest->code))
                        return -EINVAL;

                /* Some instructions need special checks */
                switch (ftest->code) {
                case BPF_ALU | BPF_DIV | BPF_K:
                case BPF_ALU | BPF_MOD | BPF_K:
                        /* Check for division by zero */
                        if (ftest->k == 0)
                                return -EINVAL;
                        break;
                case BPF_LD | BPF_MEM:
                case BPF_LDX | BPF_MEM:
                case BPF_ST:
                case BPF_STX:
                        /* Check for invalid memory addresses */
                        if (ftest->k >= BPF_MEMWORDS)
                                return -EINVAL;
                        break;
                case BPF_JMP | BPF_JA:
                        /* Note, the large ftest->k might cause loops.
                         * Compare this with conditional jumps below,
                         * where offsets are limited. --ANK (981016)
                         */
                        if (ftest->k >= (unsigned int)(flen - pc - 1))
                                return -EINVAL;
                        break;
                case BPF_JMP | BPF_JEQ | BPF_K:
                case BPF_JMP | BPF_JEQ | BPF_X:
                case BPF_JMP | BPF_JGE | BPF_K:
                case BPF_JMP | BPF_JGE | BPF_X:
                case BPF_JMP | BPF_JGT | BPF_K:
                case BPF_JMP | BPF_JGT | BPF_X:
                case BPF_JMP | BPF_JSET | BPF_K:
                case BPF_JMP | BPF_JSET | BPF_X:
                        /* Both conditionals must be safe */
                        if (pc + ftest->jt + 1 >= flen ||
                            pc + ftest->jf + 1 >= flen)
                                return -EINVAL;
                        break;
                case BPF_LD | BPF_W | BPF_ABS:
                case BPF_LD | BPF_H | BPF_ABS:
                case BPF_LD | BPF_B | BPF_ABS:
                        anc_found = false;
                        if (bpf_anc_helper(ftest) & BPF_ANC)
                                anc_found = true;
                        /* Ancillary operation unknown or unsupported */
                        if (anc_found == false && ftest->k >= SKF_AD_OFF)
                                return -EINVAL;
                }
        }

        /* Last instruction must be a RET code */
        switch (filter[flen - 1].code) {
        case BPF_RET | BPF_K:
        case BPF_RET | BPF_A:
                return check_load_and_stores(filter, flen);
        }

        return -EINVAL;
}
EXPORT_SYMBOL(bpf_check_classic);

static int bpf_prog_store_orig_filter(struct bpf_prog *fp,
                                      const struct sock_fprog *fprog)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct sock_fprog_kern *fkprog;

        fp->orig_prog = kmalloc(sizeof(*fkprog), GFP_KERNEL);
        if (!fp->orig_prog)
                return -ENOMEM;

        fkprog = fp->orig_prog;
        fkprog->len = fprog->len;
        fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
        if (!fkprog->filter) {
                kfree(fp->orig_prog);
                return -ENOMEM;
        }

        return 0;
}

static void bpf_release_orig_filter(struct bpf_prog *fp)
{
        struct sock_fprog_kern *fprog = fp->orig_prog;

        if (fprog) {
                kfree(fprog->filter);
                kfree(fprog);
        }
}

static void __bpf_prog_release(struct bpf_prog *prog)
{
        if (prog->type == BPF_PROG_TYPE_SOCKET_FILTER) {
                bpf_prog_put(prog);
        } else {
                bpf_release_orig_filter(prog);
                bpf_prog_free(prog);
        }
}

static void __sk_filter_release(struct sk_filter *fp)
{
        __bpf_prog_release(fp->prog);
        kfree(fp);
}

/**
 *      sk_filter_release_rcu - Release a socket filter by rcu_head
 *      @rcu: rcu_head that contains the sk_filter to free
 */
static void sk_filter_release_rcu(struct rcu_head *rcu)
{
        struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);

        __sk_filter_release(fp);
}

/**
 *      sk_filter_release - release a socket filter
 *      @fp: filter to remove
 *
 *      Remove a filter from a socket and release its resources.
 */
static void sk_filter_release(struct sk_filter *fp)
{
        if (atomic_dec_and_test(&fp->refcnt))
                call_rcu(&fp->rcu, sk_filter_release_rcu);
}

void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
{
        u32 filter_size = bpf_prog_size(fp->prog->len);

        atomic_sub(filter_size, &sk->sk_omem_alloc);
        sk_filter_release(fp);
}

/* try to charge the socket memory if there is space available
 * return true on success
 */
bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
        u32 filter_size = bpf_prog_size(fp->prog->len);

        /* same check as in sock_kmalloc() */
        if (filter_size <= sysctl_optmem_max &&
            atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
                atomic_inc(&fp->refcnt);
                atomic_add(filter_size, &sk->sk_omem_alloc);
                return true;
        }
        return false;
}

static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
{
        struct sock_filter *old_prog;
        struct bpf_prog *old_fp;
        int err, new_len, old_len = fp->len;

        /* We are free to overwrite insns et al right here as it
         * won't be used at this point in time anymore internally
         * after the migration to the internal BPF instruction
         * representation.
         */
        BUILD_BUG_ON(sizeof(struct sock_filter) !=
                     sizeof(struct bpf_insn));

        /* Conversion cannot happen on overlapping memory areas,
         * so we need to keep the user BPF around until the 2nd
         * pass. At this time, the user BPF is stored in fp->insns.
         */
        old_prog = kmemdup(fp->insns, old_len * sizeof(struct sock_filter),
                           GFP_KERNEL);
        if (!old_prog) {
                err = -ENOMEM;
                goto out_err;
        }

        /* 1st pass: calculate the new program length. */
        err = bpf_convert_filter(old_prog, old_len, NULL, &new_len);
        if (err)
                goto out_err_free;

        /* Expand fp for appending the new filter representation. */
        old_fp = fp;
        fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0);
        if (!fp) {
                /* The old_fp is still around in case we couldn't
                 * allocate new memory, so uncharge on that one.
                 */
                fp = old_fp;
                err = -ENOMEM;
                goto out_err_free;
        }

        fp->len = new_len;

        /* 2nd pass: remap sock_filter insns into bpf_insn insns. */
        err = bpf_convert_filter(old_prog, old_len, fp->insnsi, &new_len);
        if (err)
                /* 2nd bpf_convert_filter() can fail only if it fails
                 * to allocate memory, remapping must succeed. Note,
                 * that at this time old_fp has already been released
                 * by krealloc().
                 */
                goto out_err_free;

        bpf_prog_select_runtime(fp);

        kfree(old_prog);
        return fp;

out_err_free:
        kfree(old_prog);
out_err:
        __bpf_prog_release(fp);
        return ERR_PTR(err);
}

static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp)
{
        int err;

        fp->bpf_func = NULL;
        fp->jited = false;

        err = bpf_check_classic(fp->insns, fp->len);
        if (err) {
                __bpf_prog_release(fp);

                return ERR_PTR(err);
        }

        /* Probe if we can JIT compile the filter and if so, do
         * the compilation of the filter.
         */
        bpf_jit_compile(fp);

        /* JIT compiler couldn't process this filter, so do the
         * internal BPF translation for the optimized interpreter.
         */
        if (!fp->jited)
                fp = bpf_migrate_filter(fp);

        return fp;
}

/**
 *      bpf_prog_create - create an unattached filter
 *      @pfp: the unattached filter that is created
 *      @fprog: the filter program
 *
 * Create a filter independent of any socket. We first run some
 * sanity checks on it to make sure it does not explode on us later.
 * If an error occurs or there is insufficient memory for the filter
 * a negative errno code is returned. On success the return is zero.
 */
int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        struct bpf_prog *fp;

        /* Make sure new filter is there and in the right amounts. */
        if (fprog->filter == NULL)
                return -EINVAL;

        fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
        if (!fp)
                return -ENOMEM;

        memcpy(fp->insns, fprog->filter, fsize);

        fp->len = fprog->len;
        /* Since unattached filters are not copied back to user
         * space through sk_get_filter(), we do not need to hold
         * a copy here, and can spare us the work.
         */
        fp->orig_prog = NULL;

        /* bpf_prepare_filter() already takes care of freeing
         * memory in case something goes wrong.
         */
        fp = bpf_prepare_filter(fp);
        if (IS_ERR(fp))
                return PTR_ERR(fp);

        *pfp = fp;
        return 0;
}
EXPORT_SYMBOL_GPL(bpf_prog_create);

void bpf_prog_destroy(struct bpf_prog *fp)
{
        __bpf_prog_release(fp);
}
EXPORT_SYMBOL_GPL(bpf_prog_destroy);

static int __sk_attach_prog(struct bpf_prog *prog, struct sock *sk)
{
        struct sk_filter *fp, *old_fp;

        fp = kmalloc(sizeof(*fp), GFP_KERNEL);
        if (!fp)
                return -ENOMEM;

        fp->prog = prog;
        atomic_set(&fp->refcnt, 0);

        if (!sk_filter_charge(sk, fp)) {
                kfree(fp);
                return -ENOMEM;
        }

        old_fp = rcu_dereference_protected(sk->sk_filter,
                                           sock_owned_by_user(sk));
        rcu_assign_pointer(sk->sk_filter, fp);

        if (old_fp)
                sk_filter_uncharge(sk, old_fp);

        return 0;
}

/**
 *      sk_attach_filter - attach a socket filter
 *      @fprog: the filter program
 *      @sk: the socket to use
 *
 * Attach the user's filter code. We first run some sanity checks on
 * it to make sure it does not explode on us later. If an error
 * occurs or there is insufficient memory for the filter a negative
 * errno code is returned. On success the return is zero.
 */
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
        unsigned int fsize = bpf_classic_proglen(fprog);
        unsigned int bpf_fsize = bpf_prog_size(fprog->len);
        struct bpf_prog *prog;
        int err;

        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return -EPERM;

        /* Make sure new filter is there and in the right amounts. */
        if (fprog->filter == NULL)
                return -EINVAL;

        prog = bpf_prog_alloc(bpf_fsize, 0);
        if (!prog)
                return -ENOMEM;

        if (copy_from_user(prog->insns, fprog->filter, fsize)) {
                __bpf_prog_free(prog);
                return -EFAULT;
        }

        prog->len = fprog->len;

        err = bpf_prog_store_orig_filter(prog, fprog);
        if (err) {
                __bpf_prog_free(prog);
                return -ENOMEM;
        }

        /* bpf_prepare_filter() already takes care of freeing
         * memory in case something goes wrong.
         */
        prog = bpf_prepare_filter(prog);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        err = __sk_attach_prog(prog, sk);
        if (err < 0) {
                __bpf_prog_release(prog);
                return err;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(sk_attach_filter);

int sk_attach_bpf(u32 ufd, struct sock *sk)
{
        struct bpf_prog *prog;
        int err;

        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return -EPERM;

        prog = bpf_prog_get(ufd);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        if (prog->type != BPF_PROG_TYPE_SOCKET_FILTER) {
                bpf_prog_put(prog);
                return -EINVAL;
        }

        err = __sk_attach_prog(prog, sk);
        if (err < 0) {
                bpf_prog_put(prog);
                return err;
        }

        return 0;
}

/**
 *      bpf_skb_clone_not_writable - is the header of a clone not writable
 *      @skb: buffer to check
 *      @len: length up to which to write, can be negative
 *
 *      Returns true if modifying the header part of the cloned buffer
 *      does require the data to be copied. I.e. this version works with
 *      negative lengths needed for eBPF case!
 */
static bool bpf_skb_clone_unwritable(const struct sk_buff *skb, int len)
{
        return skb_header_cloned(skb) ||
               (int) skb_headroom(skb) + len > skb->hdr_len;
}

#define BPF_RECOMPUTE_CSUM(flags)       ((flags) & 1)

static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
{
        struct sk_buff *skb = (struct sk_buff *) (long) r1;
        int offset = (int) r2;
        void *from = (void *) (long) r3;
        unsigned int len = (unsigned int) r4;
        char buf[16];
        void *ptr;

        /* bpf verifier guarantees that:
         * 'from' pointer points to bpf program stack
         * 'len' bytes of it were initialized
         * 'len' > 0
         * 'skb' is a valid pointer to 'struct sk_buff'
         *
         * so check for invalid 'offset' and too large 'len'
         */
        if (unlikely((u32) offset > 0xffff || len > sizeof(buf)))
                return -EFAULT;

        offset -= skb->data - skb_mac_header(skb);
        if (unlikely(skb_cloned(skb) &&
                     bpf_skb_clone_unwritable(skb, offset + len)))
                return -EFAULT;

        ptr = skb_header_pointer(skb, offset, len, buf);
        if (unlikely(!ptr))
                return -EFAULT;

        if (BPF_RECOMPUTE_CSUM(flags))
                skb_postpull_rcsum(skb, ptr, len);

        memcpy(ptr, from, len);

        if (ptr == buf)
                /* skb_store_bits cannot return -EFAULT here */
                skb_store_bits(skb, offset, ptr, len);

        if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
                skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
        return 0;
}

const struct bpf_func_proto bpf_skb_store_bytes_proto = {
        .func           = bpf_skb_store_bytes,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_PTR_TO_STACK,
        .arg4_type      = ARG_CONST_STACK_SIZE,
        .arg5_type      = ARG_ANYTHING,
};

#define BPF_HEADER_FIELD_SIZE(flags)    ((flags) & 0x0f)
#define BPF_IS_PSEUDO_HEADER(flags)     ((flags) & 0x10)

static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
{
        struct sk_buff *skb = (struct sk_buff *) (long) r1;
        int offset = (int) r2;
        __sum16 sum, *ptr;

        if (unlikely((u32) offset > 0xffff))
                return -EFAULT;

        offset -= skb->data - skb_mac_header(skb);
        if (unlikely(skb_cloned(skb) &&
                     bpf_skb_clone_unwritable(skb, offset + sizeof(sum))))
                return -EFAULT;

        ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
        if (unlikely(!ptr))
                return -EFAULT;

        switch (BPF_HEADER_FIELD_SIZE(flags)) {
        case 2:
                csum_replace2(ptr, from, to);
                break;
        case 4:
                csum_replace4(ptr, from, to);
                break;
        default:
                return -EINVAL;
        }

        if (ptr == &sum)
                /* skb_store_bits guaranteed to not return -EFAULT here */
                skb_store_bits(skb, offset, ptr, sizeof(sum));

        return 0;
}

const struct bpf_func_proto bpf_l3_csum_replace_proto = {
        .func           = bpf_l3_csum_replace,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
        .arg5_type      = ARG_ANYTHING,
};

static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
{
        struct sk_buff *skb = (struct sk_buff *) (long) r1;
        u32 is_pseudo = BPF_IS_PSEUDO_HEADER(flags);
        int offset = (int) r2;
        __sum16 sum, *ptr;

        if (unlikely((u32) offset > 0xffff))
                return -EFAULT;

        offset -= skb->data - skb_mac_header(skb);
        if (unlikely(skb_cloned(skb) &&
                     bpf_skb_clone_unwritable(skb, offset + sizeof(sum))))
                return -EFAULT;

        ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
        if (unlikely(!ptr))
                return -EFAULT;

        switch (BPF_HEADER_FIELD_SIZE(flags)) {
        case 2:
                inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
                break;
        case 4:
                inet_proto_csum_replace4(ptr, skb, from, to, is_pseudo);
                break;
        default:
                return -EINVAL;
        }

        if (ptr == &sum)
                /* skb_store_bits guaranteed to not return -EFAULT here */
                skb_store_bits(skb, offset, ptr, sizeof(sum));

        return 0;
}

const struct bpf_func_proto bpf_l4_csum_replace_proto = {
        .func           = bpf_l4_csum_replace,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_ANYTHING,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
        .arg5_type      = ARG_ANYTHING,
};

static const struct bpf_func_proto *
sk_filter_func_proto(enum bpf_func_id func_id)
{
        switch (func_id) {
        case BPF_FUNC_map_lookup_elem:
                return &bpf_map_lookup_elem_proto;
        case BPF_FUNC_map_update_elem:
                return &bpf_map_update_elem_proto;
        case BPF_FUNC_map_delete_elem:
                return &bpf_map_delete_elem_proto;
        case BPF_FUNC_get_prandom_u32:
                return &bpf_get_prandom_u32_proto;
        case BPF_FUNC_get_smp_processor_id:
                return &bpf_get_smp_processor_id_proto;
        default:
                return NULL;
        }
}

static const struct bpf_func_proto *
tc_cls_act_func_proto(enum bpf_func_id func_id)
{
        switch (func_id) {
        case BPF_FUNC_skb_store_bytes:
                return &bpf_skb_store_bytes_proto;
        case BPF_FUNC_l3_csum_replace:
                return &bpf_l3_csum_replace_proto;
        case BPF_FUNC_l4_csum_replace:
                return &bpf_l4_csum_replace_proto;
        default:
                return sk_filter_func_proto(func_id);
        }
}

static bool sk_filter_is_valid_access(int off, int size,
                                      enum bpf_access_type type)
{
        /* only read is allowed */
        if (type != BPF_READ)
                return false;

        /* check bounds */
        if (off < 0 || off >= sizeof(struct __sk_buff))
                return false;

        /* disallow misaligned access */
        if (off % size != 0)
                return false;

        /* all __sk_buff fields are __u32 */
        if (size != 4)
                return false;

        return true;
}

static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
                                        struct bpf_insn *insn_buf)
{
        struct bpf_insn *insn = insn_buf;

        switch (ctx_off) {
        case offsetof(struct __sk_buff, len):
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);

                *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
                                      offsetof(struct sk_buff, len));
                break;

        case offsetof(struct __sk_buff, protocol):
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);

                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, protocol));
                break;

        case offsetof(struct __sk_buff, vlan_proto):
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_proto) != 2);

                *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
                                      offsetof(struct sk_buff, vlan_proto));
                break;

        case offsetof(struct __sk_buff, priority):
                BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, priority) != 4);

                *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
                                      offsetof(struct sk_buff, priority));
                break;

        case offsetof(struct __sk_buff, mark):
                return convert_skb_access(SKF_AD_MARK, dst_reg, src_reg, insn);

        case offsetof(struct __sk_buff, pkt_type):
                return convert_skb_access(SKF_AD_PKTTYPE, dst_reg, src_reg, insn);

        case offsetof(struct __sk_buff, queue_mapping):
                return convert_skb_access(SKF_AD_QUEUE, dst_reg, src_reg, insn);

        case offsetof(struct __sk_buff, vlan_present):
                return convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
                                          dst_reg, src_reg, insn);

        case offsetof(struct __sk_buff, vlan_tci):
                return convert_skb_access(SKF_AD_VLAN_TAG,
                                          dst_reg, src_reg, insn);
        }

        return insn - insn_buf;
}

static const struct bpf_verifier_ops sk_filter_ops = {
        .get_func_proto = sk_filter_func_proto,
        .is_valid_access = sk_filter_is_valid_access,
        .convert_ctx_access = sk_filter_convert_ctx_access,
};

static const struct bpf_verifier_ops tc_cls_act_ops = {
        .get_func_proto = tc_cls_act_func_proto,
        .is_valid_access = sk_filter_is_valid_access,
        .convert_ctx_access = sk_filter_convert_ctx_access,
};

static struct bpf_prog_type_list sk_filter_type __read_mostly = {
        .ops = &sk_filter_ops,
        .type = BPF_PROG_TYPE_SOCKET_FILTER,
};

static struct bpf_prog_type_list sched_cls_type __read_mostly = {
        .ops = &tc_cls_act_ops,
        .type = BPF_PROG_TYPE_SCHED_CLS,
};

static struct bpf_prog_type_list sched_act_type __read_mostly = {
        .ops = &tc_cls_act_ops,
        .type = BPF_PROG_TYPE_SCHED_ACT,
};

static int __init register_sk_filter_ops(void)
{
        bpf_register_prog_type(&sk_filter_type);
        bpf_register_prog_type(&sched_cls_type);
        bpf_register_prog_type(&sched_act_type);

        return 0;
}
late_initcall(register_sk_filter_ops);

int sk_detach_filter(struct sock *sk)
{
        int ret = -ENOENT;
        struct sk_filter *filter;

        if (sock_flag(sk, SOCK_FILTER_LOCKED))
                return -EPERM;

        filter = rcu_dereference_protected(sk->sk_filter,
                                           sock_owned_by_user(sk));
        if (filter) {
                RCU_INIT_POINTER(sk->sk_filter, NULL);
                sk_filter_uncharge(sk, filter);
                ret = 0;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(sk_detach_filter);

int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
                  unsigned int len)
{
        struct sock_fprog_kern *fprog;
        struct sk_filter *filter;
        int ret = 0;

        lock_sock(sk);
        filter = rcu_dereference_protected(sk->sk_filter,
                                           sock_owned_by_user(sk));
        if (!filter)
                goto out;

        /* We're copying the filter that has been originally attached,
         * so no conversion/decode needed anymore.
         */
        fprog = filter->prog->orig_prog;

        ret = fprog->len;
        if (!len)
                /* User space only enquires number of filter blocks. */
                goto out;

        ret = -EINVAL;
        if (len < fprog->len)
                goto out;

        ret = -EFAULT;
        if (copy_to_user(ubuf, fprog->filter, bpf_classic_proglen(fprog)))
                goto out;

        /* Instead of bytes, the API requests to return the number
         * of filter blocks.
         */
        ret = fprog->len;
out:
        release_sock(sk);
        return ret;
}