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authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alexander.Levin@microsoft.com; x-microsoft-antispam-message-info: 1ZIQ2dyR0QpAa3Q56Azm1m38+6/eCuPaDX4Ih2KFHImNvF84zSrtzidpds3rKJiLOY7eES4X2fLqNgbGpJlaNb+3tICMg2Nq0vkgpP/61OLuBipt+K+UHpYQHcl9RaepOeqt2vajARQln5JUQfmkd0DbQLHLUANBkB75mqSChEnaux2merrlzhPz53y/028ff7cbF+nnHwaz1lRpWXevoRZPnxGPltCKij2v+nE72KBCwqHJ1fegIbHYDkPXcE1ClTDvj5tWjXUaF1FI79LSON5S7BtaE9wJ8Iq9c+USJnJ6UxupTPhB3KJXTiJKxirwbIifOurPUaCmGW9HYacNDQ== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 367554f7-d4cb-46c8-69dc-08d58db2bdf2 X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Mar 2018 16:00:45.1820 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0933 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Ming Lei [ Upstream commit fb350e0ad99359768e1e80b4784692031ec340e4 ] In both elevator_switch_mq() and blk_mq_update_nr_hw_queues(), sched tags can be allocated, and q->nr_hw_queue is used, and race is inevitable, for example: blk_mq_init_sched() may trigger use-after-free on hctx, which is freed in blk_mq_realloc_hw_ctxs() when nr_hw_queues is decreased. This patch fixes the race be holding q->sysfs_lock. Reviewed-by: Christoph Hellwig Reported-by: Yi Zhang Tested-by: Yi Zhang Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index a1bef12dd4c4..ac09f61af52c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1907,6 +1907,9 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_= set *set, struct blk_mq_hw_ctx **hctxs =3D q->queue_hw_ctx; =20 blk_mq_sysfs_unregister(q); + + /* protect against switching io scheduler */ + mutex_lock(&q->sysfs_lock); for (i =3D 0; i < set->nr_hw_queues; i++) { int node; =20 @@ -1956,6 +1959,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_= set *set, } } q->nr_hw_queues =3D i; + mutex_unlock(&q->sysfs_lock); blk_mq_sysfs_register(q); } =20 --=20 2.14.1