On Wed, Jan 11, 2017 at 10:24:06AM +0200, Amir Goldstein wrote:
> This changes fixes an assertion hit when fuzzing on-disk
> i_mode values.
>
> The easy case to fix is when changing an empty file
> i_mode to S_IFDIR. In this case, xfs_dinode_verify()
> detects an illegal zero size for directory and fails
> to load the inode structure from disk.
>
> For the case of non empty file whose i_mode is changed
> to S_IFDIR, the ASSERT() statement in xfs_dir2_isblock()
> is replaced with return -EFSCORRUPTED, to avoid interacting
> with corrupted jusk also when XFS_DEBUG is disabled.
>
> Suggested-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_dir2.c | 3 ++-
> fs/xfs/libxfs/xfs_inode_buf.c | 7 +++++--
> 2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
> index c58d72c..4f7913f 100644
> --- a/fs/xfs/libxfs/xfs_dir2.c
> +++ b/fs/xfs/libxfs/xfs_dir2.c
> @@ -631,7 +631,8 @@ xfs_dir2_isblock(
> if ((rval = xfs_bmap_last_offset(args->dp, &last, XFS_DATA_FORK)))
> return rval;
> rval = XFS_FSB_TO_B(args->dp->i_mount, last) == args->geo->blksize;
> - ASSERT(rval == 0 || args->dp->i_d.di_size == args->geo->blksize);
> + if (rval != 0 && args->dp->i_d.di_size != args->geo->blksize)
> + return -EFSCORRUPTED;
> *vp = rval;
> return 0;
> }
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index dd483e2..0091ac3 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -386,6 +386,7 @@ xfs_dinode_verify(
> xfs_ino_t ino,
> struct xfs_dinode *dip)
> {
> + uint16_t mode;
> uint16_t flags;
> uint64_t flags2;
>
> @@ -396,8 +397,10 @@ xfs_dinode_verify(
> if (be64_to_cpu(dip->di_size) & (1ULL << 63))
> return false;
>
> - /* No zero-length symlinks. */
> - if (S_ISLNK(be16_to_cpu(dip->di_mode)) && dip->di_size == 0)
> + mode = be16_to_cpu(dip->di_mode);
> +
> + /* No zero-length symlinks/dirs. */
> + if ((S_ISLNK(mode) || S_ISDIR(mode)) && dip->di_size == 0)
Drat, I just hit this with the fuzzer tests, so I'll pull this in
for rc5. Good work! :)
--D
> return false;
>
> /* only version 3 or greater inodes are extensively verified here */
> --
> 2.7.4
>
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