ext4: fix possible use-after-free in ext4_remove_li_request()
We need to take reference to the s_li_request after we take a mutex,
because it might be freed since then, hence result in accessing old
already freed memory. Also we should protect the whole
ext4_remove_li_request() because ext4_li_info might be in the process of
being freed in ext4_lazyinit_thread().
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index fd51a4a..ed5e80e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2735,14 +2735,16 @@
static void ext4_unregister_li_request(struct super_block *sb)
{
- struct ext4_li_request *elr = EXT4_SB(sb)->s_li_request;
-
- if (!ext4_li_info)
+ mutex_lock(&ext4_li_mtx);
+ if (!ext4_li_info) {
+ mutex_unlock(&ext4_li_mtx);
return;
+ }
mutex_lock(&ext4_li_info->li_list_mtx);
- ext4_remove_li_request(elr);
+ ext4_remove_li_request(EXT4_SB(sb)->s_li_request);
mutex_unlock(&ext4_li_info->li_list_mtx);
+ mutex_unlock(&ext4_li_mtx);
}
static struct task_struct *ext4_lazyinit_task;