xfs: xfs_rtbuf_get should check the bmapi_read results

The xfs_rtbuf_get function should check the block mapping it gets back
from bmapi_read.  If there are no mappings or the mapping isn't a real
extent, we should return -EFSCORRUPTED rather than trying to read a
garbage value.  We also require realtime bitmap blocks to be real,
written allocations.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>

diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 106be2d0bb88cb44fda2ab4979b15c39c2fd64c7..7712f282d172229f96470b7be4d52d4a09d69f32 100644 (file)
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -90,6 +90,9 @@ xfs_rtbuf_get(
        if (error)
                return error;
 
+       if (nmap == 0 || !xfs_bmap_is_real_extent(&map))
+               return -EFSCORRUPTED;
+
        ASSERT(map.br_startblock != NULLFSBLOCK);
        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                                   XFS_FSB_TO_DADDR(mp, map.br_startblock),