xfs: validate inode di_forkoff

Verify the inode di_forkoff, lifted from xfs_repair's
process_check_inode_forkoff().

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 30d1d60f1d46..09d9c8cfa4a0 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -415,6 +415,31 @@ xfs_dinode_verify_fork(
         return NULL;
 }
 
+static xfs_failaddr_t
+xfs_dinode_verify_forkoff(
+        struct xfs_dinode       *dip,
+        struct xfs_mount        *mp)
+{
+        if (!XFS_DFORK_Q(dip))
+                return NULL;
+
+        switch (dip->di_format)  {
+        case XFS_DINODE_FMT_DEV:
+                if (dip->di_forkoff != (roundup(sizeof(xfs_dev_t), 8) >> 3))
+                        return __this_address;
+                break;
+        case XFS_DINODE_FMT_LOCAL:      /* fall through ... */
+        case XFS_DINODE_FMT_EXTENTS:    /* fall through ... */
+        case XFS_DINODE_FMT_BTREE:
+                if (dip->di_forkoff >= (XFS_LITINO(mp, dip->di_version) >> 3))
+                        return __this_address;
+                break;
+        default:
+                return __this_address;
+        }
+        return NULL;
+}
+
 xfs_failaddr_t
 xfs_dinode_verify(
         struct xfs_mount        *mp,
@@ -470,6 +495,11 @@ xfs_dinode_verify(
         if (mode && (flags & XFS_DIFLAG_REALTIME) && !mp->m_rtdev_targp)
                 return __this_address;
 
+        /* check for illegal values of forkoff */
+        fa = xfs_dinode_verify_forkoff(dip, mp);
+        if (fa)
+                return fa;
+
         /* Do we have appropriate data fork formats for the mode? */
         switch (mode & S_IFMT) {
         case S_IFIFO: