xfs: sanity check directory inode di_size

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@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
index c58d72c220f58593cd05b90b3227f1ecb4f2d06f..4f7913f84b28c78b30c6925298711144893819ce 100644 (file)
--- 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 dd483e2767f7a38a4dfef5c063148430364b4aaf..0091ac3f52410cae043ef5992c2396a11b1d7a56 100644 (file)
--- 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)
                return false;
 
        /* only version 3 or greater inodes are extensively verified here */