From: lei lu llfamsec@gmail.com
[ Upstream commit 0c7fcdb6d06cdf8b19b57c17605215b06afa864a ]
This adds sanity checks for xfs_dir2_data_unused and xfs_dir2_data_entry to make sure don't stray beyond valid memory region. Before patching, the loop simply checks that the start offset of the dup and dep is within the range. So in a crafted image, if last entry is xfs_dir2_data_unused, we can change dup->length to dup->length-1 and leave 1 byte of space. In the next traversal, this space will be considered as dup or dep. We may encounter an out of bound read when accessing the fixed members.
In the patch, we make sure that the remaining bytes large enough to hold an unused entry before accessing xfs_dir2_data_unused and xfs_dir2_data_unused is XFS_DIR2_DATA_ALIGN byte aligned. We also make sure that the remaining bytes large enough to hold a dirent with a single-byte name before accessing xfs_dir2_data_entry.
Signed-off-by: lei lu llfamsec@gmail.com Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Chandan Babu R chandanbabu@kernel.org Signed-off-by: Leah Rumancik leah.rumancik@gmail.com Acked-by: "Darrick J. Wong" djwong@kernel.org --- fs/xfs/libxfs/xfs_dir2_data.c | 31 ++++++++++++++++++++++++++----- fs/xfs/libxfs/xfs_dir2_priv.h | 7 +++++++ 2 files changed, 33 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c index dbcf58979a59..e1d5da6d8d4a 100644 --- a/fs/xfs/libxfs/xfs_dir2_data.c +++ b/fs/xfs/libxfs/xfs_dir2_data.c @@ -175,78 +175,99 @@ __xfs_dir3_data_check( * Loop over the data/unused entries. */ while (offset < end) { struct xfs_dir2_data_unused *dup = bp->b_addr + offset; struct xfs_dir2_data_entry *dep = bp->b_addr + offset; + unsigned int reclen; + + /* + * Are the remaining bytes large enough to hold an + * unused entry? + */ + if (offset > end - xfs_dir2_data_unusedsize(1)) + return __this_address;
/* * If it's unused, look for the space in the bestfree table. * If we find it, account for that, else make sure it * doesn't need to be there. */ if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) { xfs_failaddr_t fa;
+ reclen = xfs_dir2_data_unusedsize( + be16_to_cpu(dup->length)); if (lastfree != 0) return __this_address; - if (offset + be16_to_cpu(dup->length) > end) + if (be16_to_cpu(dup->length) != reclen) + return __this_address; + if (offset + reclen > end) return __this_address; if (be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)) != offset) return __this_address; fa = xfs_dir2_data_freefind_verify(hdr, bf, dup, &dfp); if (fa) return fa; if (dfp) { i = (int)(dfp - bf); if ((freeseen & (1 << i)) != 0) return __this_address; freeseen |= 1 << i; } else { if (be16_to_cpu(dup->length) > be16_to_cpu(bf[2].length)) return __this_address; } - offset += be16_to_cpu(dup->length); + offset += reclen; lastfree = 1; continue; } + + /* + * This is not an unused entry. Are the remaining bytes + * large enough for a dirent with a single-byte name? + */ + if (offset > end - xfs_dir2_data_entsize(mp, 1)) + return __this_address; + /* * It's a real entry. Validate the fields. * If this is a block directory then make sure it's * in the leaf section of the block. * The linear search is crude but this is DEBUG code. */ if (dep->namelen == 0) return __this_address; - if (!xfs_verify_dir_ino(mp, be64_to_cpu(dep->inumber))) + reclen = xfs_dir2_data_entsize(mp, dep->namelen); + if (offset + reclen > end) return __this_address; - if (offset + xfs_dir2_data_entsize(mp, dep->namelen) > end) + if (!xfs_verify_dir_ino(mp, be64_to_cpu(dep->inumber))) return __this_address; if (be16_to_cpu(*xfs_dir2_data_entry_tag_p(mp, dep)) != offset) return __this_address; if (xfs_dir2_data_get_ftype(mp, dep) >= XFS_DIR3_FT_MAX) return __this_address; count++; lastfree = 0; if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC) || hdr->magic == cpu_to_be32(XFS_DIR3_BLOCK_MAGIC)) { addr = xfs_dir2_db_off_to_dataptr(geo, geo->datablk, (xfs_dir2_data_aoff_t) ((char *)dep - (char *)hdr)); name.name = dep->name; name.len = dep->namelen; hash = xfs_dir2_hashname(mp, &name); for (i = 0; i < be32_to_cpu(btp->count); i++) { if (be32_to_cpu(lep[i].address) == addr && be32_to_cpu(lep[i].hashval) == hash) break; } if (i >= be32_to_cpu(btp->count)) return __this_address; } - offset += xfs_dir2_data_entsize(mp, dep->namelen); + offset += reclen; } /* * Need to have seen all the entries and all the bestfree slots. */ if (freeseen != 7) diff --git a/fs/xfs/libxfs/xfs_dir2_priv.h b/fs/xfs/libxfs/xfs_dir2_priv.h index 7404a9ff1a92..9046d08554e9 100644 --- a/fs/xfs/libxfs/xfs_dir2_priv.h +++ b/fs/xfs/libxfs/xfs_dir2_priv.h @@ -185,10 +185,17 @@ void xfs_dir2_sf_put_ftype(struct xfs_mount *mp,
/* xfs_dir2_readdir.c */ extern int xfs_readdir(struct xfs_trans *tp, struct xfs_inode *dp, struct dir_context *ctx, size_t bufsize);
+static inline unsigned int +xfs_dir2_data_unusedsize( + unsigned int len) +{ + return round_up(len, XFS_DIR2_DATA_ALIGN); +} + static inline unsigned int xfs_dir2_data_entsize( struct xfs_mount *mp, unsigned int namelen) {