From a62936210525da2f46ae264e0bf9680eafac176e Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 29 Oct 2013 22:11:56 +1100 Subject: [PATCH] xfs: validity check the directory block leaf entry count The directory block format verifier fails to check that the leaf entry count is in a valid range, and so if it is corrupted then it can lead to derefencing a pointer outside the block buffer. While we can't exactly validate the count without first walking the directory block, we can ensure the count lands in the valid area within the directory block and hence avoid out-of-block references. Signed-off-by: Dave Chinner Reviewed-by: Ben Myers Signed-off-by: Ben Myers --- fs/xfs/xfs_dir2_data.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_dir2_data.c b/fs/xfs/xfs_dir2_data.c index 18e920c86be6..70acff4ee173 100644 --- a/fs/xfs/xfs_dir2_data.c +++ b/fs/xfs/xfs_dir2_data.c @@ -65,7 +65,6 @@ __xfs_dir3_data_check( const struct xfs_dir_ops *ops; mp = bp->b_target->bt_mount; - hdr = bp->b_addr; /* * We can be passed a null dp here from a verifier, so we need to go the @@ -73,12 +72,25 @@ __xfs_dir3_data_check( */ ops = xfs_dir_get_ops(mp, dp); + hdr = bp->b_addr; + p = (char *)ops->data_entry_p(hdr); + switch (hdr->magic) { case cpu_to_be32(XFS_DIR3_BLOCK_MAGIC): case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC): btp = xfs_dir2_block_tail_p(mp, hdr); lep = xfs_dir2_block_leaf_p(btp); endp = (char *)lep; + + /* + * The number of leaf entries is limited by the size of the + * block and the amount of space used by the data entries. + * We don't know how much space is used by the data entries yet, + * so just ensure that the count falls somewhere inside the + * block right now. + */ + XFS_WANT_CORRUPTED_RETURN(be32_to_cpu(btp->count) < + ((char *)btp - p) / sizeof(struct xfs_dir2_leaf_entry)); break; case cpu_to_be32(XFS_DIR3_DATA_MAGIC): case cpu_to_be32(XFS_DIR2_DATA_MAGIC): @@ -88,13 +100,12 @@ __xfs_dir3_data_check( XFS_ERROR_REPORT("Bad Magic", XFS_ERRLEVEL_LOW, mp); return EFSCORRUPTED; } - bf = ops->data_bestfree_p(hdr); - p = (char *)ops->data_entry_p(hdr); - count = lastfree = freeseen = 0; /* * Account for zero bestfree entries. */ + bf = ops->data_bestfree_p(hdr); + count = lastfree = freeseen = 0; if (!bf[0].length) { XFS_WANT_CORRUPTED_RETURN(!bf[0].offset); freeseen |= 1 << 0; -- 2.20.1