// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * af_alg: User-space algorithm interface
 *
 * This file provides the user-space API for algorithms.
 *
 * Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <linux/atomic.h>
#include <crypto/if_alg.h>
#include <linux/crypto.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/rwsem.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/security.h>

struct alg_type_list {
        const struct af_alg_type *type;
        struct list_head list;
};

static atomic_long_t alg_memory_allocated;

static struct proto alg_proto = {
        .name                   = "ALG",
        .owner                  = THIS_MODULE,
        .memory_allocated       = &alg_memory_allocated,
        .obj_size               = sizeof(struct alg_sock),
};

static LIST_HEAD(alg_types);
static DECLARE_RWSEM(alg_types_sem);

static const struct af_alg_type *alg_get_type(const char *name)
{
        const struct af_alg_type *type = ERR_PTR(-ENOENT);
        struct alg_type_list *node;

        down_read(&alg_types_sem);
        list_for_each_entry(node, &alg_types, list) {
                if (strcmp(node->type->name, name))
                        continue;

                if (try_module_get(node->type->owner))
                        type = node->type;
                break;
        }
        up_read(&alg_types_sem);

        return type;
}

int af_alg_register_type(const struct af_alg_type *type)
{
        struct alg_type_list *node;
        int err = -EEXIST;

        down_write(&alg_types_sem);
        list_for_each_entry(node, &alg_types, list) {
                if (!strcmp(node->type->name, type->name))
                        goto unlock;
        }

        node = kmalloc(sizeof(*node), GFP_KERNEL);
        err = -ENOMEM;
        if (!node)
                goto unlock;

        type->ops->owner = THIS_MODULE;
        if (type->ops_nokey)
                type->ops_nokey->owner = THIS_MODULE;
        node->type = type;
        list_add(&node->list, &alg_types);
        err = 0;

unlock:
        up_write(&alg_types_sem);

        return err;
}
EXPORT_SYMBOL_GPL(af_alg_register_type);

int af_alg_unregister_type(const struct af_alg_type *type)
{
        struct alg_type_list *node;
        int err = -ENOENT;

        down_write(&alg_types_sem);
        list_for_each_entry(node, &alg_types, list) {
                if (strcmp(node->type->name, type->name))
                        continue;

                list_del(&node->list);
                kfree(node);
                err = 0;
                break;
        }
        up_write(&alg_types_sem);

        return err;
}
EXPORT_SYMBOL_GPL(af_alg_unregister_type);

static void alg_do_release(const struct af_alg_type *type, void *private)
{
        if (!type)
                return;

        type->release(private);
        module_put(type->owner);
}

int af_alg_release(struct socket *sock)
{
        if (sock->sk) {
                sock_put(sock->sk);
                sock->sk = NULL;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(af_alg_release);

void af_alg_release_parent(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        unsigned int nokey = atomic_read(&ask->nokey_refcnt);

        sk = ask->parent;
        ask = alg_sk(sk);

        if (nokey)
                atomic_dec(&ask->nokey_refcnt);

        if (atomic_dec_and_test(&ask->refcnt))
                sock_put(sk);
}
EXPORT_SYMBOL_GPL(af_alg_release_parent);

static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
        const u32 allowed = CRYPTO_ALG_KERN_DRIVER_ONLY;
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct sockaddr_alg_new *sa = (void *)uaddr;
        const struct af_alg_type *type;
        void *private;
        int err;

        if (sock->state == SS_CONNECTED)
                return -EINVAL;

        BUILD_BUG_ON(offsetof(struct sockaddr_alg_new, salg_name) !=
                     offsetof(struct sockaddr_alg, salg_name));
        BUILD_BUG_ON(offsetof(struct sockaddr_alg, salg_name) != sizeof(*sa));

        if (addr_len < sizeof(*sa) + 1)
                return -EINVAL;

        /* If caller uses non-allowed flag, return error. */
        if ((sa->salg_feat & ~allowed) || (sa->salg_mask & ~allowed))
                return -EINVAL;

        sa->salg_type[sizeof(sa->salg_type) - 1] = 0;
        sa->salg_name[addr_len - sizeof(*sa) - 1] = 0;

        type = alg_get_type(sa->salg_type);
        if (PTR_ERR(type) == -ENOENT) {
                request_module("algif-%s", sa->salg_type);
                type = alg_get_type(sa->salg_type);
        }

        if (IS_ERR(type))
                return PTR_ERR(type);

        private = type->bind(sa->salg_name, sa->salg_feat, sa->salg_mask);
        if (IS_ERR(private)) {
                module_put(type->owner);
                return PTR_ERR(private);
        }

        err = -EBUSY;
        lock_sock(sk);
        if (atomic_read(&ask->refcnt))
                goto unlock;

        swap(ask->type, type);
        swap(ask->private, private);

        err = 0;

unlock:
        release_sock(sk);

        alg_do_release(type, private);

        return err;
}

static int alg_setkey(struct sock *sk, sockptr_t ukey, unsigned int keylen)
{
        struct alg_sock *ask = alg_sk(sk);
        const struct af_alg_type *type = ask->type;
        u8 *key;
        int err;

        key = sock_kmalloc(sk, keylen, GFP_KERNEL);
        if (!key)
                return -ENOMEM;

        err = -EFAULT;
        if (copy_from_sockptr(key, ukey, keylen))
                goto out;

        err = type->setkey(ask->private, key, keylen);

out:
        sock_kzfree_s(sk, key, keylen);

        return err;
}

static int alg_setsockopt(struct socket *sock, int level, int optname,
                          sockptr_t optval, unsigned int optlen)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        const struct af_alg_type *type;
        int err = -EBUSY;

        lock_sock(sk);
        if (atomic_read(&ask->refcnt) != atomic_read(&ask->nokey_refcnt))
                goto unlock;

        type = ask->type;

        err = -ENOPROTOOPT;
        if (level != SOL_ALG || !type)
                goto unlock;

        switch (optname) {
        case ALG_SET_KEY:
                if (sock->state == SS_CONNECTED)
                        goto unlock;
                if (!type->setkey)
                        goto unlock;

                err = alg_setkey(sk, optval, optlen);
                break;
        case ALG_SET_AEAD_AUTHSIZE:
                if (sock->state == SS_CONNECTED)
                        goto unlock;
                if (!type->setauthsize)
                        goto unlock;
                err = type->setauthsize(ask->private, optlen);
                break;
        case ALG_SET_DRBG_ENTROPY:
                if (sock->state == SS_CONNECTED)
                        goto unlock;
                if (!type->setentropy)
                        goto unlock;

                err = type->setentropy(ask->private, optval, optlen);
        }

unlock:
        release_sock(sk);

        return err;
}

int af_alg_accept(struct sock *sk, struct socket *newsock, bool kern)
{
        struct alg_sock *ask = alg_sk(sk);
        const struct af_alg_type *type;
        struct sock *sk2;
        unsigned int nokey;
        int err;

        lock_sock(sk);
        type = ask->type;

        err = -EINVAL;
        if (!type)
                goto unlock;

        sk2 = sk_alloc(sock_net(sk), PF_ALG, GFP_KERNEL, &alg_proto, kern);
        err = -ENOMEM;
        if (!sk2)
                goto unlock;

        sock_init_data(newsock, sk2);
        security_sock_graft(sk2, newsock);
        security_sk_clone(sk, sk2);

        /*
         * newsock->ops assigned here to allow type->accept call to override
         * them when required.
         */
        newsock->ops = type->ops;
        err = type->accept(ask->private, sk2);

        nokey = err == -ENOKEY;
        if (nokey && type->accept_nokey)
                err = type->accept_nokey(ask->private, sk2);

        if (err)
                goto unlock;

        if (atomic_inc_return_relaxed(&ask->refcnt) == 1)
                sock_hold(sk);
        if (nokey) {
                atomic_inc(&ask->nokey_refcnt);
                atomic_set(&alg_sk(sk2)->nokey_refcnt, 1);
        }
        alg_sk(sk2)->parent = sk;
        alg_sk(sk2)->type = type;

        newsock->state = SS_CONNECTED;

        if (nokey)
                newsock->ops = type->ops_nokey;

        err = 0;

unlock:
        release_sock(sk);

        return err;
}
EXPORT_SYMBOL_GPL(af_alg_accept);

static int alg_accept(struct socket *sock, struct socket *newsock, int flags,
                      bool kern)
{
        return af_alg_accept(sock->sk, newsock, kern);
}

static const struct proto_ops alg_proto_ops = {
        .family         =       PF_ALG,
        .owner          =       THIS_MODULE,

        .connect        =       sock_no_connect,
        .socketpair     =       sock_no_socketpair,
        .getname        =       sock_no_getname,
        .ioctl          =       sock_no_ioctl,
        .listen         =       sock_no_listen,
        .shutdown       =       sock_no_shutdown,
        .mmap           =       sock_no_mmap,
        .sendpage       =       sock_no_sendpage,
        .sendmsg        =       sock_no_sendmsg,
        .recvmsg        =       sock_no_recvmsg,

        .bind           =       alg_bind,
        .release        =       af_alg_release,
        .setsockopt     =       alg_setsockopt,
        .accept         =       alg_accept,
};

static void alg_sock_destruct(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);

        alg_do_release(ask->type, ask->private);
}

static int alg_create(struct net *net, struct socket *sock, int protocol,
                      int kern)
{
        struct sock *sk;
        int err;

        if (sock->type != SOCK_SEQPACKET)
                return -ESOCKTNOSUPPORT;
        if (protocol != 0)
                return -EPROTONOSUPPORT;

        err = -ENOMEM;
        sk = sk_alloc(net, PF_ALG, GFP_KERNEL, &alg_proto, kern);
        if (!sk)
                goto out;

        sock->ops = &alg_proto_ops;
        sock_init_data(sock, sk);

        sk->sk_destruct = alg_sock_destruct;

        return 0;
out:
        return err;
}

static const struct net_proto_family alg_family = {
        .family =       PF_ALG,
        .create =       alg_create,
        .owner  =       THIS_MODULE,
};

int af_alg_make_sg(struct af_alg_sgl *sgl, struct iov_iter *iter, int len)
{
        size_t off;
        ssize_t n;
        int npages, i;

        n = iov_iter_get_pages(iter, sgl->pages, len, ALG_MAX_PAGES, &off);
        if (n < 0)
                return n;

        npages = DIV_ROUND_UP(off + n, PAGE_SIZE);
        if (WARN_ON(npages == 0))
                return -EINVAL;
        /* Add one extra for linking */
        sg_init_table(sgl->sg, npages + 1);

        for (i = 0, len = n; i < npages; i++) {
                int plen = min_t(int, len, PAGE_SIZE - off);

                sg_set_page(sgl->sg + i, sgl->pages[i], plen, off);

                off = 0;
                len -= plen;
        }
        sg_mark_end(sgl->sg + npages - 1);
        sgl->npages = npages;

        return n;
}
EXPORT_SYMBOL_GPL(af_alg_make_sg);

static void af_alg_link_sg(struct af_alg_sgl *sgl_prev,
                           struct af_alg_sgl *sgl_new)
{
        sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
        sg_chain(sgl_prev->sg, sgl_prev->npages + 1, sgl_new->sg);
}

void af_alg_free_sg(struct af_alg_sgl *sgl)
{
        int i;

        for (i = 0; i < sgl->npages; i++)
                put_page(sgl->pages[i]);
}
EXPORT_SYMBOL_GPL(af_alg_free_sg);

static int af_alg_cmsg_send(struct msghdr *msg, struct af_alg_control *con)
{
        struct cmsghdr *cmsg;

        for_each_cmsghdr(cmsg, msg) {
                if (!CMSG_OK(msg, cmsg))
                        return -EINVAL;
                if (cmsg->cmsg_level != SOL_ALG)
                        continue;

                switch (cmsg->cmsg_type) {
                case ALG_SET_IV:
                        if (cmsg->cmsg_len < CMSG_LEN(sizeof(*con->iv)))
                                return -EINVAL;
                        con->iv = (void *)CMSG_DATA(cmsg);
                        if (cmsg->cmsg_len < CMSG_LEN(con->iv->ivlen +
                                                      sizeof(*con->iv)))
                                return -EINVAL;
                        break;

                case ALG_SET_OP:
                        if (cmsg->cmsg_len < CMSG_LEN(sizeof(u32)))
                                return -EINVAL;
                        con->op = *(u32 *)CMSG_DATA(cmsg);
                        break;

                case ALG_SET_AEAD_ASSOCLEN:
                        if (cmsg->cmsg_len < CMSG_LEN(sizeof(u32)))
                                return -EINVAL;
                        con->aead_assoclen = *(u32 *)CMSG_DATA(cmsg);
                        break;

                default:
                        return -EINVAL;
                }
        }

        return 0;
}

/**
 * af_alg_alloc_tsgl - allocate the TX SGL
 *
 * @sk: socket of connection to user space
 * Return: 0 upon success, < 0 upon error
 */
static int af_alg_alloc_tsgl(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct af_alg_tsgl *sgl;
        struct scatterlist *sg = NULL;

        sgl = list_entry(ctx->tsgl_list.prev, struct af_alg_tsgl, list);
        if (!list_empty(&ctx->tsgl_list))
                sg = sgl->sg;

        if (!sg || sgl->cur >= MAX_SGL_ENTS) {
                sgl = sock_kmalloc(sk,
                                   struct_size(sgl, sg, (MAX_SGL_ENTS + 1)),
                                   GFP_KERNEL);
                if (!sgl)
                        return -ENOMEM;

                sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
                sgl->cur = 0;

                if (sg)
                        sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);

                list_add_tail(&sgl->list, &ctx->tsgl_list);
        }

        return 0;
}

/**
 * af_alg_count_tsgl - Count number of TX SG entries
 *
 * The counting starts from the beginning of the SGL to @bytes. If
 * an @offset is provided, the counting of the SG entries starts at the @offset.
 *
 * @sk: socket of connection to user space
 * @bytes: Count the number of SG entries holding given number of bytes.
 * @offset: Start the counting of SG entries from the given offset.
 * Return: Number of TX SG entries found given the constraints
 */
unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes, size_t offset)
{
        const struct alg_sock *ask = alg_sk(sk);
        const struct af_alg_ctx *ctx = ask->private;
        const struct af_alg_tsgl *sgl;
        unsigned int i;
        unsigned int sgl_count = 0;

        if (!bytes)
                return 0;

        list_for_each_entry(sgl, &ctx->tsgl_list, list) {
                const struct scatterlist *sg = sgl->sg;

                for (i = 0; i < sgl->cur; i++) {
                        size_t bytes_count;

                        /* Skip offset */
                        if (offset >= sg[i].length) {
                                offset -= sg[i].length;
                                bytes -= sg[i].length;
                                continue;
                        }

                        bytes_count = sg[i].length - offset;

                        offset = 0;
                        sgl_count++;

                        /* If we have seen requested number of bytes, stop */
                        if (bytes_count >= bytes)
                                return sgl_count;

                        bytes -= bytes_count;
                }
        }

        return sgl_count;
}
EXPORT_SYMBOL_GPL(af_alg_count_tsgl);

/**
 * af_alg_pull_tsgl - Release the specified buffers from TX SGL
 *
 * If @dst is non-null, reassign the pages to @dst. The caller must release
 * the pages. If @dst_offset is given only reassign the pages to @dst starting
 * at the @dst_offset (byte). The caller must ensure that @dst is large
 * enough (e.g. by using af_alg_count_tsgl with the same offset).
 *
 * @sk: socket of connection to user space
 * @used: Number of bytes to pull from TX SGL
 * @dst: If non-NULL, buffer is reassigned to dst SGL instead of releasing. The
 *       caller must release the buffers in dst.
 * @dst_offset: Reassign the TX SGL from given offset. All buffers before
 *              reaching the offset is released.
 */
void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst,
                      size_t dst_offset)
{
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct af_alg_tsgl *sgl;
        struct scatterlist *sg;
        unsigned int i, j = 0;

        while (!list_empty(&ctx->tsgl_list)) {
                sgl = list_first_entry(&ctx->tsgl_list, struct af_alg_tsgl,
                                       list);
                sg = sgl->sg;

                for (i = 0; i < sgl->cur; i++) {
                        size_t plen = min_t(size_t, used, sg[i].length);
                        struct page *page = sg_page(sg + i);

                        if (!page)
                                continue;

                        /*
                         * Assumption: caller created af_alg_count_tsgl(len)
                         * SG entries in dst.
                         */
                        if (dst) {
                                if (dst_offset >= plen) {
                                        /* discard page before offset */
                                        dst_offset -= plen;
                                } else {
                                        /* reassign page to dst after offset */
                                        get_page(page);
                                        sg_set_page(dst + j, page,
                                                    plen - dst_offset,
                                                    sg[i].offset + dst_offset);
                                        dst_offset = 0;
                                        j++;
                                }
                        }

                        sg[i].length -= plen;
                        sg[i].offset += plen;

                        used -= plen;
                        ctx->used -= plen;

                        if (sg[i].length)
                                return;

                        put_page(page);
                        sg_assign_page(sg + i, NULL);
                }

                list_del(&sgl->list);
                sock_kfree_s(sk, sgl, struct_size(sgl, sg, MAX_SGL_ENTS + 1));
        }

        if (!ctx->used)
                ctx->merge = 0;
        ctx->init = ctx->more;
}
EXPORT_SYMBOL_GPL(af_alg_pull_tsgl);

/**
 * af_alg_free_areq_sgls - Release TX and RX SGLs of the request
 *
 * @areq: Request holding the TX and RX SGL
 */
static void af_alg_free_areq_sgls(struct af_alg_async_req *areq)
{
        struct sock *sk = areq->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct af_alg_rsgl *rsgl, *tmp;
        struct scatterlist *tsgl;
        struct scatterlist *sg;
        unsigned int i;

        list_for_each_entry_safe(rsgl, tmp, &areq->rsgl_list, list) {
                atomic_sub(rsgl->sg_num_bytes, &ctx->rcvused);
                af_alg_free_sg(&rsgl->sgl);
                list_del(&rsgl->list);
                if (rsgl != &areq->first_rsgl)
                        sock_kfree_s(sk, rsgl, sizeof(*rsgl));
        }

        tsgl = areq->tsgl;
        if (tsgl) {
                for_each_sg(tsgl, sg, areq->tsgl_entries, i) {
                        if (!sg_page(sg))
                                continue;
                        put_page(sg_page(sg));
                }

                sock_kfree_s(sk, tsgl, areq->tsgl_entries * sizeof(*tsgl));
        }
}

/**
 * af_alg_wait_for_wmem - wait for availability of writable memory
 *
 * @sk: socket of connection to user space
 * @flags: If MSG_DONTWAIT is set, then only report if function would sleep
 * Return: 0 when writable memory is available, < 0 upon error
 */
static int af_alg_wait_for_wmem(struct sock *sk, unsigned int flags)
{
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        int err = -ERESTARTSYS;
        long timeout;

        if (flags & MSG_DONTWAIT)
                return -EAGAIN;

        sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);

        add_wait_queue(sk_sleep(sk), &wait);
        for (;;) {
                if (signal_pending(current))
                        break;
                timeout = MAX_SCHEDULE_TIMEOUT;
                if (sk_wait_event(sk, &timeout, af_alg_writable(sk), &wait)) {
                        err = 0;
                        break;
                }
        }
        remove_wait_queue(sk_sleep(sk), &wait);

        return err;
}

/**
 * af_alg_wmem_wakeup - wakeup caller when writable memory is available
 *
 * @sk: socket of connection to user space
 */
void af_alg_wmem_wakeup(struct sock *sk)
{
        struct socket_wq *wq;

        if (!af_alg_writable(sk))
                return;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (skwq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, EPOLLIN |
                                                           EPOLLRDNORM |
                                                           EPOLLRDBAND);
        sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(af_alg_wmem_wakeup);

/**
 * af_alg_wait_for_data - wait for availability of TX data
 *
 * @sk: socket of connection to user space
 * @flags: If MSG_DONTWAIT is set, then only report if function would sleep
 * @min: Set to minimum request size if partial requests are allowed.
 * Return: 0 when writable memory is available, < 0 upon error
 */
int af_alg_wait_for_data(struct sock *sk, unsigned flags, unsigned min)
{
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        long timeout;
        int err = -ERESTARTSYS;

        if (flags & MSG_DONTWAIT)
                return -EAGAIN;

        sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);

        add_wait_queue(sk_sleep(sk), &wait);
        for (;;) {
                if (signal_pending(current))
                        break;
                timeout = MAX_SCHEDULE_TIMEOUT;
                if (sk_wait_event(sk, &timeout,
                                  ctx->init && (!ctx->more ||
                                                (min && ctx->used >= min)),
                                  &wait)) {
                        err = 0;
                        break;
                }
        }
        remove_wait_queue(sk_sleep(sk), &wait);

        sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);

        return err;
}
EXPORT_SYMBOL_GPL(af_alg_wait_for_data);

/**
 * af_alg_data_wakeup - wakeup caller when new data can be sent to kernel
 *
 * @sk: socket of connection to user space
 */
static void af_alg_data_wakeup(struct sock *sk)
{
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct socket_wq *wq;

        if (!ctx->used)
                return;

        rcu_read_lock();
        wq = rcu_dereference(sk->sk_wq);
        if (skwq_has_sleeper(wq))
                wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
                                                           EPOLLRDNORM |
                                                           EPOLLRDBAND);
        sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
        rcu_read_unlock();
}

/**
 * af_alg_sendmsg - implementation of sendmsg system call handler
 *
 * The sendmsg system call handler obtains the user data and stores it
 * in ctx->tsgl_list. This implies allocation of the required numbers of
 * struct af_alg_tsgl.
 *
 * In addition, the ctx is filled with the information sent via CMSG.
 *
 * @sock: socket of connection to user space
 * @msg: message from user space
 * @size: size of message from user space
 * @ivsize: the size of the IV for the cipher operation to verify that the
 *         user-space-provided IV has the right size
 * Return: the number of copied data upon success, < 0 upon error
 */
int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
                   unsigned int ivsize)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct af_alg_tsgl *sgl;
        struct af_alg_control con = {};
        long copied = 0;
        bool enc = false;
        bool init = false;
        int err = 0;

        if (msg->msg_controllen) {
                err = af_alg_cmsg_send(msg, &con);
                if (err)
                        return err;

                init = true;
                switch (con.op) {
                case ALG_OP_ENCRYPT:
                        enc = true;
                        break;
                case ALG_OP_DECRYPT:
                        enc = false;
                        break;
                default:
                        return -EINVAL;
                }

                if (con.iv && con.iv->ivlen != ivsize)
                        return -EINVAL;
        }

        lock_sock(sk);
        if (ctx->init && !ctx->more) {
                if (ctx->used) {
                        err = -EINVAL;
                        goto unlock;
                }

                pr_info_once(
                        "%s sent an empty control message without MSG_MORE.\n",
                        current->comm);
        }
        ctx->init = true;

        if (init) {
                ctx->enc = enc;
                if (con.iv)
                        memcpy(ctx->iv, con.iv->iv, ivsize);

                ctx->aead_assoclen = con.aead_assoclen;
        }

        while (size) {
                struct scatterlist *sg;
                size_t len = size;
                size_t plen;

                /* use the existing memory in an allocated page */
                if (ctx->merge) {
                        sgl = list_entry(ctx->tsgl_list.prev,
                                         struct af_alg_tsgl, list);
                        sg = sgl->sg + sgl->cur - 1;
                        len = min_t(size_t, len,
                                    PAGE_SIZE - sg->offset - sg->length);

                        err = memcpy_from_msg(page_address(sg_page(sg)) +
                                              sg->offset + sg->length,
                                              msg, len);
                        if (err)
                                goto unlock;

                        sg->length += len;
                        ctx->merge = (sg->offset + sg->length) &
                                     (PAGE_SIZE - 1);

                        ctx->used += len;
                        copied += len;
                        size -= len;
                        continue;
                }

                if (!af_alg_writable(sk)) {
                        err = af_alg_wait_for_wmem(sk, msg->msg_flags);
                        if (err)
                                goto unlock;
                }

                /* allocate a new page */
                len = min_t(unsigned long, len, af_alg_sndbuf(sk));

                err = af_alg_alloc_tsgl(sk);
                if (err)
                        goto unlock;

                sgl = list_entry(ctx->tsgl_list.prev, struct af_alg_tsgl,
                                 list);
                sg = sgl->sg;
                if (sgl->cur)
                        sg_unmark_end(sg + sgl->cur - 1);

                do {
                        unsigned int i = sgl->cur;

                        plen = min_t(size_t, len, PAGE_SIZE);

                        sg_assign_page(sg + i, alloc_page(GFP_KERNEL));
                        if (!sg_page(sg + i)) {
                                err = -ENOMEM;
                                goto unlock;
                        }

                        err = memcpy_from_msg(page_address(sg_page(sg + i)),
                                              msg, plen);
                        if (err) {
                                __free_page(sg_page(sg + i));
                                sg_assign_page(sg + i, NULL);
                                goto unlock;
                        }

                        sg[i].length = plen;
                        len -= plen;
                        ctx->used += plen;
                        copied += plen;
                        size -= plen;
                        sgl->cur++;
                } while (len && sgl->cur < MAX_SGL_ENTS);

                if (!size)
                        sg_mark_end(sg + sgl->cur - 1);

                ctx->merge = plen & (PAGE_SIZE - 1);
        }

        err = 0;

        ctx->more = msg->msg_flags & MSG_MORE;

unlock:
        af_alg_data_wakeup(sk);
        release_sock(sk);

        return copied ?: err;
}
EXPORT_SYMBOL_GPL(af_alg_sendmsg);

/**
 * af_alg_sendpage - sendpage system call handler
 * @sock: socket of connection to user space to write to
 * @page: data to send
 * @offset: offset into page to begin sending
 * @size: length of data
 * @flags: message send/receive flags
 *
 * This is a generic implementation of sendpage to fill ctx->tsgl_list.
 */
ssize_t af_alg_sendpage(struct socket *sock, struct page *page,
                        int offset, size_t size, int flags)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        struct af_alg_tsgl *sgl;
        int err = -EINVAL;

        if (flags & MSG_SENDPAGE_NOTLAST)
                flags |= MSG_MORE;

        lock_sock(sk);

        if (!ctx->more && ctx->used)
                goto unlock;

        if (!size)
                goto done;

        if (!af_alg_writable(sk)) {
                err = af_alg_wait_for_wmem(sk, flags);
                if (err)
                        goto unlock;
        }

        err = af_alg_alloc_tsgl(sk);
        if (err)
                goto unlock;

        ctx->merge = 0;
        sgl = list_entry(ctx->tsgl_list.prev, struct af_alg_tsgl, list);

        if (sgl->cur)
                sg_unmark_end(sgl->sg + sgl->cur - 1);

        sg_mark_end(sgl->sg + sgl->cur);

        get_page(page);
        sg_set_page(sgl->sg + sgl->cur, page, size, offset);
        sgl->cur++;
        ctx->used += size;

done:
        ctx->more = flags & MSG_MORE;

unlock:
        af_alg_data_wakeup(sk);
        release_sock(sk);

        return err ?: size;
}
EXPORT_SYMBOL_GPL(af_alg_sendpage);

/**
 * af_alg_free_resources - release resources required for crypto request
 * @areq: Request holding the TX and RX SGL
 */
void af_alg_free_resources(struct af_alg_async_req *areq)
{
        struct sock *sk = areq->sk;

        af_alg_free_areq_sgls(areq);
        sock_kfree_s(sk, areq, areq->areqlen);
}
EXPORT_SYMBOL_GPL(af_alg_free_resources);

/**
 * af_alg_async_cb - AIO callback handler
 * @_req: async request info
 * @err: if non-zero, error result to be returned via ki_complete();
 *       otherwise return the AIO output length via ki_complete().
 *
 * This handler cleans up the struct af_alg_async_req upon completion of the
 * AIO operation.
 *
 * The number of bytes to be generated with the AIO operation must be set
 * in areq->outlen before the AIO callback handler is invoked.
 */
void af_alg_async_cb(struct crypto_async_request *_req, int err)
{
        struct af_alg_async_req *areq = _req->data;
        struct sock *sk = areq->sk;
        struct kiocb *iocb = areq->iocb;
        unsigned int resultlen;

        /* Buffer size written by crypto operation. */
        resultlen = areq->outlen;

        af_alg_free_resources(areq);
        sock_put(sk);

        iocb->ki_complete(iocb, err ? err : (int)resultlen, 0);
}
EXPORT_SYMBOL_GPL(af_alg_async_cb);

/**
 * af_alg_poll - poll system call handler
 * @file: file pointer
 * @sock: socket to poll
 * @wait: poll_table
 */
__poll_t af_alg_poll(struct file *file, struct socket *sock,
                         poll_table *wait)
{
        struct sock *sk = sock->sk;
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        __poll_t mask;

        sock_poll_wait(file, sock, wait);
        mask = 0;

        if (!ctx->more || ctx->used)
                mask |= EPOLLIN | EPOLLRDNORM;

        if (af_alg_writable(sk))
                mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;

        return mask;
}
EXPORT_SYMBOL_GPL(af_alg_poll);

/**
 * af_alg_alloc_areq - allocate struct af_alg_async_req
 *
 * @sk: socket of connection to user space
 * @areqlen: size of struct af_alg_async_req + crypto_*_reqsize
 * Return: allocated data structure or ERR_PTR upon error
 */
struct af_alg_async_req *af_alg_alloc_areq(struct sock *sk,
                                           unsigned int areqlen)
{
        struct af_alg_async_req *areq = sock_kmalloc(sk, areqlen, GFP_KERNEL);

        if (unlikely(!areq))
                return ERR_PTR(-ENOMEM);

        areq->areqlen = areqlen;
        areq->sk = sk;
        areq->last_rsgl = NULL;
        INIT_LIST_HEAD(&areq->rsgl_list);
        areq->tsgl = NULL;
        areq->tsgl_entries = 0;

        return areq;
}
EXPORT_SYMBOL_GPL(af_alg_alloc_areq);

/**
 * af_alg_get_rsgl - create the RX SGL for the output data from the crypto
 *                   operation
 *
 * @sk: socket of connection to user space
 * @msg: user space message
 * @flags: flags used to invoke recvmsg with
 * @areq: instance of the cryptographic request that will hold the RX SGL
 * @maxsize: maximum number of bytes to be pulled from user space
 * @outlen: number of bytes in the RX SGL
 * Return: 0 on success, < 0 upon error
 */
int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
                    struct af_alg_async_req *areq, size_t maxsize,
                    size_t *outlen)
{
        struct alg_sock *ask = alg_sk(sk);
        struct af_alg_ctx *ctx = ask->private;
        size_t len = 0;

        while (maxsize > len && msg_data_left(msg)) {
                struct af_alg_rsgl *rsgl;
                size_t seglen;
                int err;

                /* limit the amount of readable buffers */
                if (!af_alg_readable(sk))
                        break;

                seglen = min_t(size_t, (maxsize - len),
                               msg_data_left(msg));

                if (list_empty(&areq->rsgl_list)) {
                        rsgl = &areq->first_rsgl;
                } else {
                        rsgl = sock_kmalloc(sk, sizeof(*rsgl), GFP_KERNEL);
                        if (unlikely(!rsgl))
                                return -ENOMEM;
                }

                rsgl->sgl.npages = 0;
                list_add_tail(&rsgl->list, &areq->rsgl_list);

                /* make one iovec available as scatterlist */
                err = af_alg_make_sg(&rsgl->sgl, &msg->msg_iter, seglen);
                if (err < 0) {
                        rsgl->sg_num_bytes = 0;
                        return err;
                }

                /* chain the new scatterlist with previous one */
                if (areq->last_rsgl)
                        af_alg_link_sg(&areq->last_rsgl->sgl, &rsgl->sgl);

                areq->last_rsgl = rsgl;
                len += err;
                atomic_add(err, &ctx->rcvused);
                rsgl->sg_num_bytes = err;
                iov_iter_advance(&msg->msg_iter, err);
        }

        *outlen = len;
        return 0;
}
EXPORT_SYMBOL_GPL(af_alg_get_rsgl);

static int __init af_alg_init(void)
{
        int err = proto_register(&alg_proto, 0);

        if (err)
                goto out;

        err = sock_register(&alg_family);
        if (err != 0)
                goto out_unregister_proto;

out:
        return err;

out_unregister_proto:
        proto_unregister(&alg_proto);
        goto out;
}

static void __exit af_alg_exit(void)
{
        sock_unregister(PF_ALG);
        proto_unregister(&alg_proto);
}

module_init(af_alg_init);
module_exit(af_alg_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NETPROTO(AF_ALG);