xfs: do not use unchecked extent indices in xfs_bmapi

Make sure to only call xfs_iext_get_ext after we've validate the
extent index when moving on to the next index in xfs_bmapi.

Based on an earlier patch from Lachlan McIlroy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lachlan McIlroy <lmcilroy@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 130ec4fa5eaf..af655c1d460d 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -4825,12 +4825,13 @@ xfs_bmapi(
                 /*
                  * Else go on to the next record.
                  */
-                ep = xfs_iext_get_ext(ifp, ++lastx);
                 prev = got;
-                if (lastx >= nextents)
-                        eof = 1;
-                else
+                if (++lastx < nextents) {
+                        ep = xfs_iext_get_ext(ifp, lastx);
                         xfs_bmbt_get_all(ep, &got);
+                } else {
+                        eof = 1;
+                }
         }
         *nmap = n;
         /*