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

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index a044a9b77491..ea32d7e1d6e3 100644
--- 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;
+                        }
                 }
         }