From: Denis Rastyogin Date: Tue, 4 Mar 2025 08:39:10 +0000 (+0300) Subject: block/qed: fix use-after-free by nullifying timer pointer after free X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=2ad638a3d160923ef3dbf87c73944e6e44bdc724;p=qemu.git 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 Message-ID: <20250304083927.37681-1-gerben@altlinux.org> Signed-off-by: Stefan Hajnoczi --- 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,