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xfs: directory scrubber must walk through data block to offset 

In xfs_scrub_dir_rec, we must walk through the directory block entries
to arrive at the offset given by the hash structure.  If we blindly
trust the hash address, we can end up midway into a directory entry and
stray outside the block.  Found by lastbit fuzzing lents[3].address in
xfs/390 with KASAN enabled.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Darrick J. Wong 2018-01-16 18:54:12 -08:00
parent 638a717489
commit ce92d29ddf
5 changed files with 58 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/xfs/libxfs/xfs_dir2.h
View File

@ -340,5 +340,7 @@ xfs_dir2_leaf_tail_p(struct xfs_da_geometry *geo, struct xfs_dir2_leaf *lp)
#define XFS_READDIR_BUFSIZE (32768)
unsigned char xfs_dir3_get_dtype(struct xfs_mount *mp, uint8_t filetype);
void *xfs_dir3_data_endp(struct xfs_da_geometry *geo,
struct xfs_dir2_data_hdr *hdr);
#endif /* __XFS_DIR2_H__ */

43
fs/xfs/libxfs/xfs_dir2_data.c
View File

@ -89,7 +89,6 @@ __xfs_dir3_data_check(
case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC):
btp = xfs_dir2_block_tail_p(geo, hdr);
lep = xfs_dir2_block_leaf_p(btp);
endp = (char *)lep;
/*
* The number of leaf entries is limited by the size of the
@ -104,11 +103,13 @@ __xfs_dir3_data_check(
break;
case cpu_to_be32(XFS_DIR3_DATA_MAGIC):
case cpu_to_be32(XFS_DIR2_DATA_MAGIC):
endp = (char *)hdr + geo->blksize;
break;
default:
return __this_address;
}
endp = xfs_dir3_data_endp(geo, hdr);
if (!endp)
return __this_address;
/*
* Account for zero bestfree entries.
@ -546,7 +547,6 @@ xfs_dir2_data_freescan_int(
struct xfs_dir2_data_hdr *hdr,
int *loghead)
{
xfs_dir2_block_tail_t *btp; /* block tail */
xfs_dir2_data_entry_t *dep; /* active data entry */
xfs_dir2_data_unused_t *dup; /* unused data entry */
struct xfs_dir2_data_free *bf;
@ -568,12 +568,7 @@ xfs_dir2_data_freescan_int(
* Set up pointers.
*/
p = (char *)ops->data_entry_p(hdr);
if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC) ||
hdr->magic == cpu_to_be32(XFS_DIR3_BLOCK_MAGIC)) {
btp = xfs_dir2_block_tail_p(geo, hdr);
endp = (char *)xfs_dir2_block_leaf_p(btp);
} else
endp = (char *)hdr + geo->blksize;
endp = xfs_dir3_data_endp(geo, hdr);
/*
* Loop over the block's entries.
*/
@ -786,17 +781,9 @@ xfs_dir2_data_make_free(
/*
* Figure out where the end of the data area is.
*/
if (hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
hdr->magic == cpu_to_be32(XFS_DIR3_DATA_MAGIC))
endptr = (char *)hdr + args->geo->blksize;
else {
xfs_dir2_block_tail_t *btp; /* block tail */
endptr = xfs_dir3_data_endp(args->geo, hdr);
ASSERT(endptr != NULL);
ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC) ||
hdr->magic == cpu_to_be32(XFS_DIR3_BLOCK_MAGIC));
btp = xfs_dir2_block_tail_p(args->geo, hdr);
endptr = (char *)xfs_dir2_block_leaf_p(btp);
}
/*
* If this isn't the start of the block, then back up to
* the previous entry and see if it's free.
@ -1098,3 +1085,21 @@ xfs_dir2_data_use_free(
}
*needscanp = needscan;
}
/* Find the end of the entry data in a data/block format dir block. */
void *
xfs_dir3_data_endp(
struct xfs_da_geometry *geo,
struct xfs_dir2_data_hdr *hdr)
{
switch (hdr->magic) {
case cpu_to_be32(XFS_DIR3_BLOCK_MAGIC):
case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC):
return xfs_dir2_block_leaf_p(xfs_dir2_block_tail_p(geo, hdr));
case cpu_to_be32(XFS_DIR3_DATA_MAGIC):
case cpu_to_be32(XFS_DIR2_DATA_MAGIC):
return (char *)hdr + geo->blksize;
default:
return NULL;
}
}

4
fs/xfs/libxfs/xfs_dir2_sf.c
View File

@ -156,7 +156,6 @@ xfs_dir2_block_to_sf(
xfs_dir2_sf_hdr_t *sfhp) /* shortform directory hdr */
{
xfs_dir2_data_hdr_t *hdr; /* block header */
xfs_dir2_block_tail_t *btp; /* block tail pointer */
xfs_dir2_data_entry_t *dep; /* data entry pointer */
xfs_inode_t *dp; /* incore directory inode */
xfs_dir2_data_unused_t *dup; /* unused data pointer */
@ -192,9 +191,8 @@ xfs_dir2_block_to_sf(
/*
* Set up to loop over the block's entries.
*/
btp = xfs_dir2_block_tail_p(args->geo, hdr);
ptr = (char *)dp->d_ops->data_entry_p(hdr);
endptr = (char *)xfs_dir2_block_leaf_p(btp);
endptr = xfs_dir3_data_endp(args->geo, hdr);
sfep = xfs_dir2_sf_firstentry(sfp);
/*
* Loop over the active and unused entries.

38
fs/xfs/scrub/dir.c
View File

@ -200,6 +200,7 @@ xfs_scrub_dir_rec(
struct xfs_inode *dp = ds->dargs.dp;
struct xfs_dir2_data_entry *dent;
struct xfs_buf *bp;
char *p, *endp;
xfs_ino_t ino;
xfs_dablk_t rec_bno;
xfs_dir2_db_t db;
@ -239,8 +240,35 @@ xfs_scrub_dir_rec(
}
xfs_scrub_buffer_recheck(ds->sc, bp);
/* Retrieve the entry, sanity check it, and compare hashes. */
dent = (struct xfs_dir2_data_entry *)(((char *)bp->b_addr) + off);
/* Make sure we got a real directory entry. */
p = (char *)mp->m_dir_inode_ops->data_entry_p(bp->b_addr);
endp = xfs_dir3_data_endp(mp->m_dir_geo, bp->b_addr);
if (!endp) {
xfs_scrub_fblock_set_corrupt(ds->sc, XFS_DATA_FORK, rec_bno);
goto out_relse;
}
while (p < endp) {
struct xfs_dir2_data_entry *dep;
struct xfs_dir2_data_unused *dup;
dup = (struct xfs_dir2_data_unused *)p;
if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
p += be16_to_cpu(dup->length);
continue;
}
dep = (struct xfs_dir2_data_entry *)p;
if (dep == dent)
break;
p += mp->m_dir_inode_ops->data_entsize(dep->namelen);
}
if (p >= endp) {
xfs_scrub_fblock_set_corrupt(ds->sc, XFS_DATA_FORK, rec_bno);
goto out_relse;
}
/* Retrieve the entry, sanity check it, and compare hashes. */
ino = be64_to_cpu(dent->inumber);
hash = be32_to_cpu(ent->hashval);
tag = be16_to_cpup(dp->d_ops->data_entry_tag_p(dent));
@ -363,13 +391,7 @@ xfs_scrub_directory_data_bestfree(
/* Make sure the bestfrees are actually the best free spaces. */
ptr = (char *)d_ops->data_entry_p(bp->b_addr);
if (is_block) {
struct xfs_dir2_block_tail *btp;
btp = xfs_dir2_block_tail_p(mp->m_dir_geo, bp->b_addr);
endptr = (char *)xfs_dir2_block_leaf_p(btp);
} else
endptr = (char *)bp->b_addr + BBTOB(bp->b_length);
endptr = xfs_dir3_data_endp(mp->m_dir_geo, bp->b_addr);
/* Iterate the entries, stopping when we hit or go past the end. */
while (ptr < endptr) {

4
fs/xfs/xfs_dir2_readdir.c
View File

@ -152,7 +152,6 @@ xfs_dir2_block_getdents(
struct xfs_inode *dp = args->dp; /* incore directory inode */
xfs_dir2_data_hdr_t *hdr; /* block header */
struct xfs_buf *bp; /* buffer for block */
xfs_dir2_block_tail_t *btp; /* block tail */
xfs_dir2_data_entry_t *dep; /* block data entry */
xfs_dir2_data_unused_t *dup; /* block unused entry */
char *endptr; /* end of the data entries */
@ -185,9 +184,8 @@ xfs_dir2_block_getdents(
/*
* Set up values for the loop.
*/
btp = xfs_dir2_block_tail_p(geo, hdr);
ptr = (char *)dp->d_ops->data_entry_p(hdr);
endptr = (char *)xfs_dir2_block_leaf_p(btp);
endptr = xfs_dir3_data_endp(geo, hdr);
/*
* Loop over the data portion of the block.