ext4: fix potential NULL dereference in ext4_free_inodes_counts()

The ext4_get_group_desc() function returns NULL on error, and
ext4_free_inodes_count() function dereferences it without checking.
There is a check on the next line, but it's too late.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index a044a9b..ea32d7e 100644 (file)
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -508,10 +508,12 @@ fallback_retry:
        for (i = 0; i < ngroups; i++) {
                grp = (parent_group + i) % ngroups;
                desc = ext4_get_group_desc(sb, grp, NULL);
-               grp_free = ext4_free_inodes_count(sb, desc);
-               if (desc && grp_free && grp_free >= avefreei) {
-                       *group = grp;
-                       return 0;
+               if (desc) {
+                       grp_free = ext4_free_inodes_count(sb, desc);
+                       if (grp_free && grp_free >= avefreei) {
+                               *group = grp;
+                               return 0;
+                       }
                }
        }