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[199.106.103.254]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3417bcc031bsm3012089a91.2.2025.11.05.00.56.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Nov 2025 00:56:03 -0800 (PST) Message-ID: <8910d20d-dc47-4a12-9e83-204174154663@oss.qualcomm.com> Date: Wed, 5 Nov 2025 16:56:01 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] virtio_blk: NULL out vqs to avoid double free on failed resume From: Cong Zhang To: "Michael S. Tsirkin" , Jason Wang Cc: Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Paolo Bonzini , Stefan Hajnoczi , Jens Axboe , linux-arm-msm@vger.kernel.org, virtualization@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, pavan.kondeti@oss.qualcomm.com References: <20251021-virtio_double_free-v1-1-4dd0cfd258f1@oss.qualcomm.com> <20251021085030-mutt-send-email-mst@kernel.org> <20251022014453-mutt-send-email-mst@kernel.org> <20251022030050-mutt-send-email-mst@kernel.org> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: g0C9-W6stQatQb7iUOv6aaTYQMyxS8TE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTA1MDA2NSBTYWx0ZWRfX428irxI1S5pD EHxmr0sBROe/dCbZegYBNhzHFU/t1mrnN2CceyMp7KDx3bchbD2cB3OWYt6314N2P2dHQCJL+Yx pqRS/M+zmz3ilmm1ihFWECH1+bCb6yeEYHf/kUbufIBGquKanPobgsAjnTPi/0EgpWpthdKxSrU lASpnnIpW0AszhA2ltBfvRbhMR/fhAzKENm/HOBP9T/f9NMXxzdLqA6Z3EPVmiEAuN1uE4Hq4kF ygYTzcfwBoz+NsGYtvMgpZw8dIx/6BaYl40toFoAoCDJIrUGW1l2yWeJ3Jbfz/HJtH7Shi1rR+b J8+LJY1+h1uSP0tFWItHC5pOkBaYrQ4U82YaeFCVRlzSfpEUBVt7I2Jl+W6qj94EJI7tC5Skj4G JsYhzlkx8HaN83oVOpzsJJIq4dzPGQ== X-Authority-Analysis: v=2.4 cv=KaXfcAYD c=1 sm=1 tr=0 ts=690b1125 cx=c_pps a=RP+M6JBNLl+fLTcSJhASfg==:117 a=JYp8KDb2vCoCEuGobkYCKw==:17 a=IkcTkHD0fZMA:10 a=6UeiqGixMTsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=20KFwNOVAAAA:8 a=EUspDBNiAAAA:8 a=0_t0tbNFZAkfsDOXaUgA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=iS9zxrgQBfv6-_F4QbHw:22 X-Proofpoint-GUID: g0C9-W6stQatQb7iUOv6aaTYQMyxS8TE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-05_03,2025-11-03_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 impostorscore=0 malwarescore=0 spamscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2511050065 On 10/22/2025 4:02 PM, Cong Zhang wrote: > > > On 10/22/2025 3:01 PM, Michael S. Tsirkin wrote: >> On Wed, Oct 22, 2025 at 01:45:38AM -0400, Michael S. Tsirkin wrote: >>> On Wed, Oct 22, 2025 at 12:19:19PM +0800, Jason Wang wrote: >>>> On Tue, Oct 21, 2025 at 8:58 PM Michael S. Tsirkin wrote: >>>>> >>>>> On Tue, Oct 21, 2025 at 07:07:56PM +0800, Cong Zhang wrote: >>>>>> The vblk->vqs releases during freeze. If resume fails before vblk->vqs >>>>>> is allocated, later freeze/remove may attempt to free vqs again. >>>>>> Set vblk->vqs to NULL after freeing to avoid double free. >>>>>> >>>>>> Signed-off-by: Cong Zhang >>>>>> --- >>>>>> The patch fixes a double free issue that occurs in virtio_blk during >>>>>> freeze/resume. >>>>>> The issue is caused by: >>>>>> 1. During the first freeze, vblk->vqs is freed but pointer is not set to >>>>>> NULL. >>>>>> 2. Virtio block device fails before vblk->vqs is allocated during resume. >>>>>> 3. During the next freeze, vblk->vqs gets freed again, causing the >>>>>> double free crash. >>>>> >>>>> this part I don't get. if restore fails, how can freeze be called >>>>> again? >>>> >>>> For example, could it be triggered by the user? >>>> >>>> Thanks >>> >>> I don't know - were you able to trigger it? how? >> >> Sorry I mean the submitter of course. >> > > Let me add more details: > Autosleep is enabled in this case. When the system wakes up from > suspend, it will call virtio_device_restore. The failure happens in the > virtio_device_restore function before vblk->vqs has been allocated. The > system still gets woken up after the failure happens. Since autosleep is > enabled and there is no wakelock being held, the system will try to > suspend again. Then virtio_device_freeze will be called and causes the > issue. > Gentle reminder. Please let me know if you need any additional information. >>> >>>>> >>>>>> --- >>>>>> drivers/block/virtio_blk.c | 13 ++++++++++++- >>>>>> 1 file changed, 12 insertions(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c >>>>>> index f061420dfb10c40b21765b173fab7046aa447506..746795066d7f56a01c9a9c0344d24f9fa06841eb 100644 >>>>>> --- a/drivers/block/virtio_blk.c >>>>>> +++ b/drivers/block/virtio_blk.c >>>>>> @@ -1026,8 +1026,13 @@ static int init_vq(struct virtio_blk *vblk) >>>>>> out: >>>>>> kfree(vqs); >>>>>> kfree(vqs_info); >>>>>> - if (err) >>>>>> + if (err) { >>>>>> kfree(vblk->vqs); >>>>>> + /* >>>>>> + * Set to NULL to prevent freeing vqs again during freezing. >>>>>> + */ >>>>>> + vblk->vqs = NULL; >>>>>> + } >>>>>> return err; >>>>>> } >>>>>> >>>>> >>>>>> @@ -1598,6 +1603,12 @@ static int virtblk_freeze_priv(struct virtio_device *vdev) >>>>>> >>>>>> vdev->config->del_vqs(vdev); >>>>>> kfree(vblk->vqs); >>>>>> + /* >>>>>> + * Set to NULL to prevent freeing vqs again after a failed vqs >>>>>> + * allocation during resume. Note that kfree() already handles NULL >>>>>> + * pointers safely. >>>>>> + */ >>>>>> + vblk->vqs = NULL; >>>>>> >>>>>> return 0; >>>>>> } >>>>>> >>>>>> --- >>>>>> base-commit: 8e2755d7779a95dd61d8997ebce33ff8b1efd3fb >>>>>> change-id: 20250926-virtio_double_free-7ab880d82a17 >>>>>> >>>>>> Best regards, >>>>>> -- >>>>>> Cong Zhang >>>>> >> >