From: "Philippe Mathieu-Daudé" <philmd@linaro.org>
To: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org
Cc: qemu-block@nongnu.org, Hanna Reitz <hreitz@redhat.com>,
Kevin Wolf <kwolf@redhat.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: Re: [PATCH for-7.2] block-backend: avoid bdrv_unregister_buf() NULL pointer deref
Date: Mon, 21 Nov 2022 23:22:33 +0100 [thread overview]
Message-ID: <18e94ec0-6f79-8e7b-8a97-6d1824f83033@linaro.org> (raw)
In-Reply-To: <20221121211923.1993171-1-stefanha@redhat.com>
On 21/11/22 22:19, Stefan Hajnoczi wrote:
> bdrv_*() APIs expect a valid BlockDriverState. Calling them with bs=NULL
> leads to undefined behavior.
>
> Jonathan Cameron reported this following NULL pointer dereference when a
> VM with a virtio-blk device and a memory-backend-file object is
> terminated:
> 1. qemu_cleanup() closes all drives, setting blk->root to NULL
> 2. qemu_cleanup() calls user_creatable_cleanup(), which results in a RAM
> block notifier callback because the memory-backend-file is destroyed.
> 3. blk_unregister_buf() is called by virtio-blk's BlockRamRegistrar
> notifier callback and undefined behavior occurs.
>
> Fixes: baf422684d73 ("virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint")
> Co-authored-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> block/block-backend.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
next prev parent reply other threads:[~2022-11-21 22:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-21 21:19 [PATCH for-7.2] block-backend: avoid bdrv_unregister_buf() NULL pointer deref Stefan Hajnoczi
2022-11-21 22:22 ` Philippe Mathieu-Daudé [this message]
2022-11-22 8:21 ` Kevin Wolf
2022-11-29 20:53 ` Stefan Hajnoczi
2022-11-30 19:47 ` Stefan Hajnoczi
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