ext4: add missing brelse() in add_new_gdb_meta_bg()

mainline inclusion
from mainline-5.1-rc2
commit d64264d6218e6892edd832dc3a5a5857c2856c53
category: bugfix
bugzilla: 13110
CVE: NA

-------------------------------------------------

Currently in add_new_gdb_meta_bg() there is a missing brelse of gdb_bh
in case ext4_journal_get_write_access() fails.
Additionally kvfree() is missing in the same error path. Fix it by
moving the ext4_journal_get_write_access() before the ext4 sb update as
Ted suggested and release n_group_desc and gdb_bh in case it fails.

Fixes: 61a9c11e5e7a ("ext4: add missing brelse() add_new_gdb_meta_bg()'s error path")
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: Nluojiajun <luojiajun3@huawei.com>
Reviewed-by: Nyangerkun <yangerkun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/ext4/resize.c

@@ -932,11 +932,18 @@ static int add_new_gdb_meta_bg(struct super_block *sb,
 	memcpy(n_group_desc, o_group_desc,
 	       EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
 	n_group_desc[gdb_num] = gdb_bh;
+
+	BUFFER_TRACE(gdb_bh, "get_write_access");
+	err = ext4_journal_get_write_access(handle, gdb_bh);
+	if (err) {
+		kvfree(n_group_desc);
+		brelse(gdb_bh);
+		return err;
+	}
+
 	EXT4_SB(sb)->s_group_desc = n_group_desc;
 	EXT4_SB(sb)->s_gdb_count++;
 	kvfree(o_group_desc);
-	BUFFER_TRACE(gdb_bh, "get_write_access");
-	err = ext4_journal_get_write_access(handle, gdb_bh);
 	return err;
 }