// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/isofs/rock.c
 *
 *  (C) 1992, 1993  Eric Youngdale
 *
 *  Rock Ridge Extensions to iso9660
 */

#include <linux/slab.h>
#include <linux/pagemap.h>

#include "isofs.h"
#include "rock.h"

/*
 * These functions are designed to read the system areas of a directory record
 * and extract relevant information.  There are different functions provided
 * depending upon what information we need at the time.  One function fills
 * out an inode structure, a second one extracts a filename, a third one
 * returns a symbolic link name, and a fourth one returns the extent number
 * for the file.
 */

#define SIG(A,B) ((A) | ((B) << 8))     /* isonum_721() */

struct rock_state {
        void *buffer;
        unsigned char *chr;
        int len;
        int cont_size;
        int cont_extent;
        int cont_offset;
        int cont_loops;
        struct inode *inode;
};

/*
 * This is a way of ensuring that we have something in the system
 * use fields that is compatible with Rock Ridge.  Return zero on success.
 */

static int check_sp(struct rock_ridge *rr, struct inode *inode)
{
        if (rr->u.SP.magic[0] != 0xbe)
                return -1;
        if (rr->u.SP.magic[1] != 0xef)
                return -1;
        ISOFS_SB(inode->i_sb)->s_rock_offset = rr->u.SP.skip;
        return 0;
}

static void setup_rock_ridge(struct iso_directory_record *de,
                        struct inode *inode, struct rock_state *rs)
{
        rs->len = sizeof(struct iso_directory_record) + de->name_len[0];
        if (rs->len & 1)
                (rs->len)++;
        rs->chr = (unsigned char *)de + rs->len;
        rs->len = *((unsigned char *)de) - rs->len;
        if (rs->len < 0)
                rs->len = 0;

        if (ISOFS_SB(inode->i_sb)->s_rock_offset != -1) {
                rs->len -= ISOFS_SB(inode->i_sb)->s_rock_offset;
                rs->chr += ISOFS_SB(inode->i_sb)->s_rock_offset;
                if (rs->len < 0)
                        rs->len = 0;
        }
}

static void init_rock_state(struct rock_state *rs, struct inode *inode)
{
        memset(rs, 0, sizeof(*rs));
        rs->inode = inode;
}

/* Maximum number of Rock Ridge continuation entries */
#define RR_MAX_CE_ENTRIES 32

/*
 * Returns 0 if the caller should continue scanning, 1 if the scan must end
 * and -ve on error.
 */
static int rock_continue(struct rock_state *rs)
{
        int ret = 1;
        int blocksize = 1 << rs->inode->i_blkbits;
        const int min_de_size = offsetof(struct rock_ridge, u);

        kfree(rs->buffer);
        rs->buffer = NULL;

        if ((unsigned)rs->cont_offset > blocksize - min_de_size ||
            (unsigned)rs->cont_size > blocksize ||
            (unsigned)(rs->cont_offset + rs->cont_size) > blocksize) {
                printk(KERN_NOTICE "rock: corrupted directory entry. "
                        "extent=%d, offset=%d, size=%d\n",
                        rs->cont_extent, rs->cont_offset, rs->cont_size);
                ret = -EIO;
                goto out;
        }

        if (rs->cont_extent) {
                struct buffer_head *bh;

                rs->buffer = kmalloc(rs->cont_size, GFP_KERNEL);
                if (!rs->buffer) {
                        ret = -ENOMEM;
                        goto out;
                }
                ret = -EIO;
                if (++rs->cont_loops >= RR_MAX_CE_ENTRIES)
                        goto out;
                bh = sb_bread(rs->inode->i_sb, rs->cont_extent);
                if (bh) {
                        memcpy(rs->buffer, bh->b_data + rs->cont_offset,
                                        rs->cont_size);
                        put_bh(bh);
                        rs->chr = rs->buffer;
                        rs->len = rs->cont_size;
                        rs->cont_extent = 0;
                        rs->cont_size = 0;
                        rs->cont_offset = 0;
                        return 0;
                }
                printk("Unable to read rock-ridge attributes\n");
        }
out:
        kfree(rs->buffer);
        rs->buffer = NULL;
        return ret;
}

/*
 * We think there's a record of type `sig' at rs->chr.  Parse the signature
 * and make sure that there's really room for a record of that type.
 */
static int rock_check_overflow(struct rock_state *rs, int sig)
{
        int len;

        switch (sig) {
        case SIG('S', 'P'):
                len = sizeof(struct SU_SP_s);
                break;
        case SIG('C', 'E'):
                len = sizeof(struct SU_CE_s);
                break;
        case SIG('E', 'R'):
                len = sizeof(struct SU_ER_s);
                break;
        case SIG('R', 'R'):
                len = sizeof(struct RR_RR_s);
                break;
        case SIG('P', 'X'):
                len = sizeof(struct RR_PX_s);
                break;
        case SIG('P', 'N'):
                len = sizeof(struct RR_PN_s);
                break;
        case SIG('S', 'L'):
                len = sizeof(struct RR_SL_s);
                break;
        case SIG('N', 'M'):
                len = sizeof(struct RR_NM_s);
                break;
        case SIG('C', 'L'):
                len = sizeof(struct RR_CL_s);
                break;
        case SIG('P', 'L'):
                len = sizeof(struct RR_PL_s);
                break;
        case SIG('T', 'F'):
                len = sizeof(struct RR_TF_s);
                break;
        case SIG('Z', 'F'):
                len = sizeof(struct RR_ZF_s);
                break;
        default:
                len = 0;
                break;
        }
        len += offsetof(struct rock_ridge, u);
        if (len > rs->len) {
                printk(KERN_NOTICE "rock: directory entry would overflow "
                                "storage\n");
                printk(KERN_NOTICE "rock: sig=0x%02x, size=%d, remaining=%d\n",
                                sig, len, rs->len);
                return -EIO;
        }
        return 0;
}

/*
 * return length of name field; 0: not found, -1: to be ignored
 */
int get_rock_ridge_filename(struct iso_directory_record *de,
                            char *retname, struct inode *inode)
{
        struct rock_state rs;
        struct rock_ridge *rr;
        int sig;
        int retnamlen = 0;
        int truncate = 0;
        int ret = 0;
        char *p;
        int len;

        if (!ISOFS_SB(inode->i_sb)->s_rock)
                return 0;
        *retname = 0;

        init_rock_state(&rs, inode);
        setup_rock_ridge(de, inode, &rs);
repeat:

        while (rs.len > 2) { /* There may be one byte for padding somewhere */
                rr = (struct rock_ridge *)rs.chr;
                /*
                 * Ignore rock ridge info if rr->len is out of range, but
                 * don't return -EIO because that would make the file
                 * invisible.
                 */
                if (rr->len < 3)
                        goto out;       /* Something got screwed up here */
                sig = isonum_721(rs.chr);
                if (rock_check_overflow(&rs, sig))
                        goto eio;
                rs.chr += rr->len;
                rs.len -= rr->len;
                /*
                 * As above, just ignore the rock ridge info if rr->len
                 * is bogus.
                 */
                if (rs.len < 0)
                        goto out;       /* Something got screwed up here */

                switch (sig) {
                case SIG('R', 'R'):
                        if ((rr->u.RR.flags[0] & RR_NM) == 0)
                                goto out;
                        break;
                case SIG('S', 'P'):
                        if (check_sp(rr, inode))
                                goto out;
                        break;
                case SIG('C', 'E'):
                        rs.cont_extent = isonum_733(rr->u.CE.extent);
                        rs.cont_offset = isonum_733(rr->u.CE.offset);
                        rs.cont_size = isonum_733(rr->u.CE.size);
                        break;
                case SIG('N', 'M'):
                        if (truncate)
                                break;
                        if (rr->len < 5)
                                break;
                        /*
                         * If the flags are 2 or 4, this indicates '.' or '..'.
                         * We don't want to do anything with this, because it
                         * screws up the code that calls us.  We don't really
                         * care anyways, since we can just use the non-RR
                         * name.
                         */
                        if (rr->u.NM.flags & 6)
                                break;

                        if (rr->u.NM.flags & ~1) {
                                printk("Unsupported NM flag settings (%d)\n",
                                        rr->u.NM.flags);
                                break;
                        }
                        len = rr->len - 5;
                        if (retnamlen + len >= 254) {
                                truncate = 1;
                                break;
                        }
                        p = memchr(rr->u.NM.name, '\0', len);
                        if (unlikely(p))
                                len = p - rr->u.NM.name;
                        memcpy(retname + retnamlen, rr->u.NM.name, len);
                        retnamlen += len;
                        retname[retnamlen] = '\0';
                        break;
                case SIG('R', 'E'):
                        kfree(rs.buffer);
                        return -1;
                default:
                        break;
                }
        }
        ret = rock_continue(&rs);
        if (ret == 0)
                goto repeat;
        if (ret == 1)
                return retnamlen; /* If 0, this file did not have a NM field */
out:
        kfree(rs.buffer);
        return ret;
eio:
        ret = -EIO;
        goto out;
}

#define RR_REGARD_XA 1
#define RR_RELOC_DE 2

static int
parse_rock_ridge_inode_internal(struct iso_directory_record *de,
                                struct inode *inode, int flags)
{
        int symlink_len = 0;
        int cnt, sig;
        unsigned int reloc_block;
        struct inode *reloc;
        struct rock_ridge *rr;
        int rootflag;
        struct rock_state rs;
        int ret = 0;

        if (!ISOFS_SB(inode->i_sb)->s_rock)
                return 0;

        init_rock_state(&rs, inode);
        setup_rock_ridge(de, inode, &rs);
        if (flags & RR_REGARD_XA) {
                rs.chr += 14;
                rs.len -= 14;
                if (rs.len < 0)
                        rs.len = 0;
        }

repeat:
        while (rs.len > 2) { /* There may be one byte for padding somewhere */
                rr = (struct rock_ridge *)rs.chr;
                /*
                 * Ignore rock ridge info if rr->len is out of range, but
                 * don't return -EIO because that would make the file
                 * invisible.
                 */
                if (rr->len < 3)
                        goto out;       /* Something got screwed up here */
                sig = isonum_721(rs.chr);
                if (rock_check_overflow(&rs, sig))
                        goto eio;
                rs.chr += rr->len;
                rs.len -= rr->len;
                /*
                 * As above, just ignore the rock ridge info if rr->len
                 * is bogus.
                 */
                if (rs.len < 0)
                        goto out;       /* Something got screwed up here */

                switch (sig) {
#ifndef CONFIG_ZISOFS           /* No flag for SF or ZF */
                case SIG('R', 'R'):
                        if ((rr->u.RR.flags[0] &
                             (RR_PX | RR_TF | RR_SL | RR_CL)) == 0)
                                goto out;
                        break;
#endif
                case SIG('S', 'P'):
                        if (check_sp(rr, inode))
                                goto out;
                        break;
                case SIG('C', 'E'):
                        rs.cont_extent = isonum_733(rr->u.CE.extent);
                        rs.cont_offset = isonum_733(rr->u.CE.offset);
                        rs.cont_size = isonum_733(rr->u.CE.size);
                        break;
                case SIG('E', 'R'):
                        /* Invalid length of ER tag id? */
                        if (rr->u.ER.len_id + offsetof(struct rock_ridge, u.ER.data) > rr->len)
                                goto out;
                        ISOFS_SB(inode->i_sb)->s_rock = 1;
                        printk(KERN_DEBUG "ISO 9660 Extensions: ");
                        {
                                int p;
                                for (p = 0; p < rr->u.ER.len_id; p++)
                                        printk(KERN_CONT "%c", rr->u.ER.data[p]);
                        }
                        printk(KERN_CONT "\n");
                        break;
                case SIG('P', 'X'):
                        inode->i_mode = isonum_733(rr->u.PX.mode);
                        set_nlink(inode, isonum_733(rr->u.PX.n_links));
                        i_uid_write(inode, isonum_733(rr->u.PX.uid));
                        i_gid_write(inode, isonum_733(rr->u.PX.gid));
                        break;
                case SIG('P', 'N'):
                        {
                                int high, low;
                                high = isonum_733(rr->u.PN.dev_high);
                                low = isonum_733(rr->u.PN.dev_low);
                                /*
                                 * The Rock Ridge standard specifies that if
                                 * sizeof(dev_t) <= 4, then the high field is
                                 * unused, and the device number is completely
                                 * stored in the low field.  Some writers may
                                 * ignore this subtlety,
                                 * and as a result we test to see if the entire
                                 * device number is
                                 * stored in the low field, and use that.
                                 */
                                if ((low & ~0xff) && high == 0) {
                                        inode->i_rdev =
                                            MKDEV(low >> 8, low & 0xff);
                                } else {
                                        inode->i_rdev =
                                            MKDEV(high, low);
                                }
                        }
                        break;
                case SIG('T', 'F'):
                        /*
                         * Some RRIP writers incorrectly place ctime in the
                         * TF_CREATE field. Try to handle this correctly for
                         * either case.
                         */
                        /* Rock ridge never appears on a High Sierra disk */
                        cnt = 0;
                        if (rr->u.TF.flags & TF_CREATE) {
                                inode->i_ctime.tv_sec =
                                    iso_date(rr->u.TF.times[cnt++].time,
                                             0);
                                inode->i_ctime.tv_nsec = 0;
                        }
                        if (rr->u.TF.flags & TF_MODIFY) {
                                inode->i_mtime.tv_sec =
                                    iso_date(rr->u.TF.times[cnt++].time,
                                             0);
                                inode->i_mtime.tv_nsec = 0;
                        }
                        if (rr->u.TF.flags & TF_ACCESS) {
                                inode->i_atime.tv_sec =
                                    iso_date(rr->u.TF.times[cnt++].time,
                                             0);
                                inode->i_atime.tv_nsec = 0;
                        }
                        if (rr->u.TF.flags & TF_ATTRIBUTES) {
                                inode->i_ctime.tv_sec =
                                    iso_date(rr->u.TF.times[cnt++].time,
                                             0);
                                inode->i_ctime.tv_nsec = 0;
                        }
                        break;
                case SIG('S', 'L'):
                        {
                                int slen;
                                struct SL_component *slp;
                                struct SL_component *oldslp;
                                slen = rr->len - 5;
                                slp = &rr->u.SL.link;
                                inode->i_size = symlink_len;
                                while (slen > 1) {
                                        rootflag = 0;
                                        switch (slp->flags & ~1) {
                                        case 0:
                                                inode->i_size +=
                                                    slp->len;
                                                break;
                                        case 2:
                                                inode->i_size += 1;
                                                break;
                                        case 4:
                                                inode->i_size += 2;
                                                break;
                                        case 8:
                                                rootflag = 1;
                                                inode->i_size += 1;
                                                break;
                                        default:
                                                printk("Symlink component flag "
                                                        "not implemented\n");
                                        }
                                        slen -= slp->len + 2;
                                        oldslp = slp;
                                        slp = (struct SL_component *)
                                                (((char *)slp) + slp->len + 2);

                                        if (slen < 2) {
                                                if (((rr->u.SL.
                                                      flags & 1) != 0)
                                                    &&
                                                    ((oldslp->
                                                      flags & 1) == 0))
                                                        inode->i_size +=
                                                            1;
                                                break;
                                        }

                                        /*
                                         * If this component record isn't
                                         * continued, then append a '/'.
                                         */
                                        if (!rootflag
                                            && (oldslp->flags & 1) == 0)
                                                inode->i_size += 1;
                                }
                        }
                        symlink_len = inode->i_size;
                        break;
                case SIG('R', 'E'):
                        printk(KERN_WARNING "Attempt to read inode for "
                                        "relocated directory\n");
                        goto out;
                case SIG('C', 'L'):
                        if (flags & RR_RELOC_DE) {
                                printk(KERN_ERR
                                       "ISOFS: Recursive directory relocation "
                                       "is not supported\n");
                                goto eio;
                        }
                        reloc_block = isonum_733(rr->u.CL.location);
                        if (reloc_block == ISOFS_I(inode)->i_iget5_block &&
                            ISOFS_I(inode)->i_iget5_offset == 0) {
                                printk(KERN_ERR
                                       "ISOFS: Directory relocation points to "
                                       "itself\n");
                                goto eio;
                        }
                        ISOFS_I(inode)->i_first_extent = reloc_block;
                        reloc = isofs_iget_reloc(inode->i_sb, reloc_block, 0);
                        if (IS_ERR(reloc)) {
                                ret = PTR_ERR(reloc);
                                goto out;
                        }
                        inode->i_mode = reloc->i_mode;
                        set_nlink(inode, reloc->i_nlink);
                        inode->i_uid = reloc->i_uid;
                        inode->i_gid = reloc->i_gid;
                        inode->i_rdev = reloc->i_rdev;
                        inode->i_size = reloc->i_size;
                        inode->i_blocks = reloc->i_blocks;
                        inode->i_atime = reloc->i_atime;
                        inode->i_ctime = reloc->i_ctime;
                        inode->i_mtime = reloc->i_mtime;
                        iput(reloc);
                        break;
#ifdef CONFIG_ZISOFS
                case SIG('Z', 'F'): {
                        int algo;

                        if (ISOFS_SB(inode->i_sb)->s_nocompress)
                                break;
                        algo = isonum_721(rr->u.ZF.algorithm);
                        if (algo == SIG('p', 'z')) {
                                int block_shift =
                                        isonum_711(&rr->u.ZF.parms[1]);
                                if (block_shift > 17) {
                                        printk(KERN_WARNING "isofs: "
                                                "Can't handle ZF block "
                                                "size of 2^%d\n",
                                                block_shift);
                                } else {
                                        /*
                                         * Note: we don't change
                                         * i_blocks here
                                         */
                                        ISOFS_I(inode)->i_file_format =
                                                isofs_file_compressed;
                                        /*
                                         * Parameters to compression
                                         * algorithm (header size,
                                         * block size)
                                         */
                                        ISOFS_I(inode)->i_format_parm[0] =
                                                isonum_711(&rr->u.ZF.parms[0]);
                                        ISOFS_I(inode)->i_format_parm[1] =
                                                isonum_711(&rr->u.ZF.parms[1]);
                                        inode->i_size =
                                            isonum_733(rr->u.ZF.
                                                       real_size);
                                }
                        } else {
                                printk(KERN_WARNING
                                       "isofs: Unknown ZF compression "
                                                "algorithm: %c%c\n",
                                       rr->u.ZF.algorithm[0],
                                       rr->u.ZF.algorithm[1]);
                        }
                        break;
                }
#endif
                default:
                        break;
                }
        }
        ret = rock_continue(&rs);
        if (ret == 0)
                goto repeat;
        if (ret == 1)
                ret = 0;
out:
        kfree(rs.buffer);
        return ret;
eio:
        ret = -EIO;
        goto out;
}

static char *get_symlink_chunk(char *rpnt, struct rock_ridge *rr, char *plimit)
{
        int slen;
        int rootflag;
        struct SL_component *oldslp;
        struct SL_component *slp;
        slen = rr->len - 5;
        slp = &rr->u.SL.link;
        while (slen > 1) {
                rootflag = 0;
                switch (slp->flags & ~1) {
                case 0:
                        if (slp->len > plimit - rpnt)
                                return NULL;
                        memcpy(rpnt, slp->text, slp->len);
                        rpnt += slp->len;
                        break;
                case 2:
                        if (rpnt >= plimit)
                                return NULL;
                        *rpnt++ = '.';
                        break;
                case 4:
                        if (2 > plimit - rpnt)
                                return NULL;
                        *rpnt++ = '.';
                        *rpnt++ = '.';
                        break;
                case 8:
                        if (rpnt >= plimit)
                                return NULL;
                        rootflag = 1;
                        *rpnt++ = '/';
                        break;
                default:
                        printk("Symlink component flag not implemented (%d)\n",
                               slp->flags);
                }
                slen -= slp->len + 2;
                oldslp = slp;
                slp = (struct SL_component *)((char *)slp + slp->len + 2);

                if (slen < 2) {
                        /*
                         * If there is another SL record, and this component
                         * record isn't continued, then add a slash.
                         */
                        if ((!rootflag) && (rr->u.SL.flags & 1) &&
                            !(oldslp->flags & 1)) {
                                if (rpnt >= plimit)
                                        return NULL;
                                *rpnt++ = '/';
                        }
                        break;
                }

                /*
                 * If this component record isn't continued, then append a '/'.
                 */
                if (!rootflag && !(oldslp->flags & 1)) {
                        if (rpnt >= plimit)
                                return NULL;
                        *rpnt++ = '/';
                }
        }
        return rpnt;
}

int parse_rock_ridge_inode(struct iso_directory_record *de, struct inode *inode,
                           int relocated)
{
        int flags = relocated ? RR_RELOC_DE : 0;
        int result = parse_rock_ridge_inode_internal(de, inode, flags);

        /*
         * if rockridge flag was reset and we didn't look for attributes
         * behind eventual XA attributes, have a look there
         */
        if ((ISOFS_SB(inode->i_sb)->s_rock_offset == -1)
            && (ISOFS_SB(inode->i_sb)->s_rock == 2)) {
                result = parse_rock_ridge_inode_internal(de, inode,
                                                         flags | RR_REGARD_XA);
        }
        return result;
}

/*
 * readpage() for symlinks: reads symlink contents into the page and either
 * makes it uptodate and returns 0 or returns error (-EIO)
 */
static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct iso_inode_info *ei = ISOFS_I(inode);
        struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
        char *link = page_address(page);
        unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
        struct buffer_head *bh;
        char *rpnt = link;
        unsigned char *pnt;
        struct iso_directory_record *raw_de;
        unsigned long block, offset;
        int sig;
        struct rock_ridge *rr;
        struct rock_state rs;
        int ret;

        if (!sbi->s_rock)
                goto error;

        init_rock_state(&rs, inode);
        block = ei->i_iget5_block;
        bh = sb_bread(inode->i_sb, block);
        if (!bh)
                goto out_noread;

        offset = ei->i_iget5_offset;
        pnt = (unsigned char *)bh->b_data + offset;

        raw_de = (struct iso_directory_record *)pnt;

        /*
         * If we go past the end of the buffer, there is some sort of error.
         */
        if (offset + *pnt > bufsize)
                goto out_bad_span;

        /*
         * Now test for possible Rock Ridge extensions which will override
         * some of these numbers in the inode structure.
         */

        setup_rock_ridge(raw_de, inode, &rs);

repeat:
        while (rs.len > 2) { /* There may be one byte for padding somewhere */
                rr = (struct rock_ridge *)rs.chr;
                if (rr->len < 3)
                        goto out;       /* Something got screwed up here */
                sig = isonum_721(rs.chr);
                if (rock_check_overflow(&rs, sig))
                        goto out;
                rs.chr += rr->len;
                rs.len -= rr->len;
                if (rs.len < 0)
                        goto out;       /* corrupted isofs */

                switch (sig) {
                case SIG('R', 'R'):
                        if ((rr->u.RR.flags[0] & RR_SL) == 0)
                                goto out;
                        break;
                case SIG('S', 'P'):
                        if (check_sp(rr, inode))
                                goto out;
                        break;
                case SIG('S', 'L'):
                        rpnt = get_symlink_chunk(rpnt, rr,
                                                 link + (PAGE_SIZE - 1));
                        if (rpnt == NULL)
                                goto out;
                        break;
                case SIG('C', 'E'):
                        /* This tells is if there is a continuation record */
                        rs.cont_extent = isonum_733(rr->u.CE.extent);
                        rs.cont_offset = isonum_733(rr->u.CE.offset);
                        rs.cont_size = isonum_733(rr->u.CE.size);
                default:
                        break;
                }
        }
        ret = rock_continue(&rs);
        if (ret == 0)
                goto repeat;
        if (ret < 0)
                goto fail;

        if (rpnt == link)
                goto fail;
        brelse(bh);
        *rpnt = '\0';
        SetPageUptodate(page);
        unlock_page(page);
        return 0;

        /* error exit from macro */
out:
        kfree(rs.buffer);
        goto fail;
out_noread:
        printk("unable to read i-node block");
        goto fail;
out_bad_span:
        printk("symlink spans iso9660 blocks\n");
fail:
        brelse(bh);
error:
        SetPageError(page);
        unlock_page(page);
        return -EIO;
}

const struct address_space_operations isofs_symlink_aops = {
        .readpage = rock_ridge_symlink_readpage
};