xfs: don't allow di_size with high bit set

The on-disk field di_size is used to set i_size, which is a signed
integer of loff_t.  If the high bit of di_size is set, we'll end up with
a negative i_size, which will cause all sorts of problems.  Since the
VFS won't let us create a file with such length, we should catch them
here in the verifier too.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 134424fac434..c906e50515f0 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -392,6 +392,14 @@ xfs_dinode_verify(
         if (dip->di_magic != cpu_to_be16(XFS_DINODE_MAGIC))
                 return false;
 
+        /* don't allow invalid i_size */
+        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)
+                return false;
+
         /* only version 3 or greater inodes are extensively verified here */
         if (dip->di_version < 3)
                 return true;