From 2ad638a3d160923ef3dbf87c73944e6e44bdc724 Mon Sep 17 00:00:00 2001
From: Denis Rastyogin <gerben@altlinux.org>
Date: Tue, 4 Mar 2025 11:39:10 +0300
Subject: [PATCH] block/qed: fix use-after-free by nullifying timer pointer
after free
This error was discovered by fuzzing qemu-img.
In the QED block driver, the need_check_timer timer is freed in
bdrv_qed_detach_aio_context, but the pointer to the timer is not
set to NULL. This can lead to a use-after-free scenario
in bdrv_qed_drain_begin().
The need_check_timer pointer is set to NULL after freeing the timer.
Which helps catch this condition when checking in bdrv_qed_drain_begin().
Closes: https://gitlab.com/qemu-project/qemu/-/issues/2852
Signed-off-by: Denis Rastyogin <gerben@altlinux.org>
Message-ID: <20250304083927.37681-1-gerben@altlinux.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/qed.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/block/qed.c b/block/qed.c
index 382c9e5335..ac24449ffb 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -353,6 +353,7 @@ static void bdrv_qed_detach_aio_context(BlockDriverState *bs)
qed_cancel_need_check_timer(s);
timer_free(s->need_check_timer);
+ s->need_check_timer = NULL;
}
static void bdrv_qed_attach_aio_context(BlockDriverState *bs,
--
2.30.2