rock.c

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/*
 *  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;
    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;
}

/*
 * 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;
        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;

    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;
            }
            if ((strlen(retname) + rr->len - 5) >= 254) {
                truncate = 1;
                break;
            }
            strncat(retname, rr->u.NM.name, rr->len - 5);
            retnamlen += rr->len - 5;
            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;
}

static int
parse_rock_ridge_inode_internal(struct iso_directory_record *de,
                struct inode *inode, int regard_xa)
{
    int symlink_len = 0;
    int cnt, sig;
    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 (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'):
            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("%c", rr->u.ER.data[p]);
            }
            printk("\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'):
            ISOFS_I(inode)->i_first_extent =
                isonum_733(rr->u.CL.location);
            reloc =
                isofs_iget(inode->i_sb,
                       ISOFS_I(inode)->i_first_extent,
                       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 result = parse_rock_ridge_inode_internal(de, inode, 0);

    /*
     * 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, 14);
    }
    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 = kmap(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);
    kunmap(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);
    kunmap(page);
    unlock_page(page);
    return -EIO;
}

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