From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04220302151; Wed, 22 Oct 2025 08:10:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761120610; cv=none; b=Xi1dZ/q1Lvq65aph2DQTNoD7uyOkZt61CYi8TzjeWLJx69IreNyo24Vr/W2Wz5AldKB1qLuK7SQynlMC9xkiJt9OSxCKvFrxX/SWEC7mhxYduCoTCKPLB1ilKmIno+QMoyNvu+E4f+mR8pVjDGvuMl1SyehJ5+5DcvnRRb0oRlI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761120610; c=relaxed/simple; bh=pdjzDIyGc0Ha6pX2r3NiQ3rBH7VjgJGHYVWdUrWURzM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KKRoPhSzaXhHJQ3hoETlQ7i1QMCdTpDvTg7eVhfnvdUEkCsj4LPKh3zHguz3i0RTpTQCXk2gu3IMKnmOeMEmXSDI4UCUEe10j03CAGPO4DQS9WwvgU+em4xrjoyeDk2aUfl6ORGtYJknQtM/DjgifeBnrwYfY+VJU/u2nxUFfgM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XWitcTay; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XWitcTay" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D452C4CEF5; Wed, 22 Oct 2025 08:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1761120609; bh=pdjzDIyGc0Ha6pX2r3NiQ3rBH7VjgJGHYVWdUrWURzM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XWitcTaylUNucJ5mO2g433Pq6yk8i5gfWa6Lu2+qyhIy3ytGA9WIEF0WC6O8igclZ mvZOwCuoyTjcmzoPl+EWfFbv0+CS/R5IjyYhVuyQmiNW+l2rp0UzOAKo0oa/ktP8xK uTy/39Th4piX/543EzqvL5Vm+8a8xDJN/MYVk4wc= Date: Wed, 22 Oct 2025 10:10:07 +0200 From: Greg KH To: Li Lingfeng Cc: Sasha Levin , stable@vger.kernel.org, Zheng Qixing , Mikulas Patocka , dm-devel@lists.linux.dev, yangerkun , "zhangyi (F)" , Hou Tao Subject: Re: [PATCH 5.10.y] dm: fix NULL pointer dereference in __dm_suspend() Message-ID: <2025102252-abrasive-glamorous-465b@gregkh> References: <2025101316-favored-pulsate-a811@gregkh> <20251014030334.3868139-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Oct 22, 2025 at 04:01:04PM +0800, Li Lingfeng wrote: > Hi, > > 在 2025/10/14 11:03, Sasha Levin 写道: > > From: Zheng Qixing > > > > [ Upstream commit 8d33a030c566e1f105cd5bf27f37940b6367f3be ] > > > > There is a race condition between dm device suspend and table load that > > can lead to null pointer dereference. The issue occurs when suspend is > > invoked before table load completes: > > > > BUG: kernel NULL pointer dereference, address: 0000000000000054 > > Oops: 0000 [#1] PREEMPT SMP PTI > > CPU: 6 PID: 6798 Comm: dmsetup Not tainted 6.6.0-g7e52f5f0ca9b #62 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 > > RIP: 0010:blk_mq_wait_quiesce_done+0x0/0x50 > > Call Trace: > > > > blk_mq_quiesce_queue+0x2c/0x50 > > dm_stop_queue+0xd/0x20 > > __dm_suspend+0x130/0x330 > > dm_suspend+0x11a/0x180 > > dev_suspend+0x27e/0x560 > > ctl_ioctl+0x4cf/0x850 > > dm_ctl_ioctl+0xd/0x20 > > vfs_ioctl+0x1d/0x50 > > __se_sys_ioctl+0x9b/0xc0 > > __x64_sys_ioctl+0x19/0x30 > > x64_sys_call+0x2c4a/0x4620 > > do_syscall_64+0x9e/0x1b0 > > > > The issue can be triggered as below: > > > > T1 T2 > > dm_suspend table_load > > __dm_suspend dm_setup_md_queue > > dm_mq_init_request_queue > > blk_mq_init_allocated_queue > > => q->mq_ops = set->ops; (1) > > dm_stop_queue / dm_wait_for_completion > > => q->tag_set NULL pointer! (2) > > => q->tag_set = set; (3) > > > > Fix this by checking if a valid table (map) exists before performing > > request-based suspend and waiting for target I/O. When map is NULL, > > skip these table-dependent suspend steps. > > > > Even when map is NULL, no I/O can reach any target because there is > > no table loaded; I/O submitted in this state will fail early in the > > DM layer. Skipping the table-dependent suspend logic in this case > > is safe and avoids NULL pointer dereferences. > > > > Fixes: c4576aed8d85 ("dm: fix request-based dm's use of dm_wait_for_completion") > > Cc: stable@vger.kernel.org > > Signed-off-by: Zheng Qixing > > Signed-off-by: Mikulas Patocka > > [ omitted DMF_QUEUE_STOPPED flag setting and braces absent in 5.15 ] > > Signed-off-by: Sasha Levin > > --- > > drivers/md/dm.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > > index 0868358a7a8d2..b51281ce15d4c 100644 > > --- a/drivers/md/dm.c > > +++ b/drivers/md/dm.c > > @@ -2457,7 +2457,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map, > > { > > bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG; > > bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG; > > - int r; > > + int r = 0; > > lockdep_assert_held(&md->suspend_lock); > > @@ -2509,7 +2509,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map, > > * Stop md->queue before flushing md->wq in case request-based > > * dm defers requests to md->wq from md->queue. > > */ > > - if (dm_request_based(md)) > > + if (map && dm_request_based(md)) > > dm_stop_queue(md->queue); > It seems that before commit 80bd4a7aab4c ("blk-mq: move the srcu_struct > used for quiescing to the tagset") was merged, blk_mq_wait_quiesce_done() > would not attempt to access q->tag_set, so in dm_stop_queue() this kind > of race condition would not cause a null pointer dereference. The change > may not be necessary for 5.10, but adding it doesn’t appear to cause any > issues either. > > flush_workqueue(md->wq); > > @@ -2519,7 +2519,8 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map, > > * We call dm_wait_for_completion to wait for all existing requests > > * to finish. > > */ > > - r = dm_wait_for_completion(md, task_state); > > + if (map) > > + r = dm_wait_for_completion(md, task_state); > The fix tag c4576aed8d85 ("dm: fix request-based dm's use of > dm_wait_for_completion") seems to correspond to the modification of > dm_wait_for_completion(). > > if (!r) > > set_bit(dmf_suspended_flag, &md->flags); > > Perhaps adding another fix tag would be more appropriate? Those tags come directly from the original commit.