xfs: check for dinode realtime flag corruption

Ramon tested XFS with a modified version of fsfuzzer and hit a NULL
pointer dereference in __xfs_get_blocks due to the RT device target
pointer being NULL.

To fix this reject inode with the realtime bit set on a a filesystem
without an RT subvolume during inode read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Reported-by: Ramon de Carvalho Valle <ramon@risesecurity.org>
Tested-by: Ramon de Carvalho Valle <ramon@risesecurity.org>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 1f22d65fed0a..da428b3fe0f5 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -343,6 +343,16 @@ xfs_iformat(
                 return XFS_ERROR(EFSCORRUPTED);
         }
 
+        if (unlikely((ip->i_d.di_flags & XFS_DIFLAG_REALTIME) &&
+                     !ip->i_mount->m_rtdev_targp)) {
+                xfs_fs_repair_cmn_err(CE_WARN, ip->i_mount,
+                        "corrupt dinode %Lu, has realtime flag set.",
+                        ip->i_ino);
+                XFS_CORRUPTION_ERROR("xfs_iformat(realtime)",
+                                     XFS_ERRLEVEL_LOW, ip->i_mount, dip);
+                return XFS_ERROR(EFSCORRUPTED);
+        }
+
         switch (ip->i_d.di_mode & S_IFMT) {
         case S_IFIFO:
         case S_IFCHR: