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 55E4D54F9B; Thu, 30 Nov 2023 16:34:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1HzVtkgm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2E58C433C8; Thu, 30 Nov 2023 16:34:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1701362067; bh=shYSt+BtU/mIQznMEx+d9n6ASBMTGfPZdlonTXW2F8c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1HzVtkgmNq+t9F41aMUzs8FS3LNp4WxQxVKOT6JS4ybJMAuCfYOtF2Sdg5HFO/1U5 iRbVLVaYmY/Qg3IjQfBhr9fg4d+BWgu03pgdqBps2G5EHxkBQ9L2Nlzcl0LqP43eig sr3BpmbVEJP8pHXVKYNQR5ZVRErT+YaeX3ZtxgPE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mikulas Patocka , Mike Snitzer , Sasha Levin Subject: [PATCH 5.15 54/69] dm-delay: fix a race between delay_presuspend and delay_bio Date: Thu, 30 Nov 2023 16:22:51 +0000 Message-ID: <20231130162134.836619848@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231130162133.035359406@linuxfoundation.org> References: <20231130162133.035359406@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka [ Upstream commit 6fc45b6ed921dc00dfb264dc08c7d67ee63d2656 ] In delay_presuspend, we set the atomic variable may_delay and then stop the timer and flush pending bios. The intention here is to prevent the delay target from re-arming the timer again. However, this test is racy. Suppose that one thread goes to delay_bio, sees that dc->may_delay is one and proceeds; now, another thread executes delay_presuspend, it sets dc->may_delay to zero, deletes the timer and flushes pending bios. Then, the first thread continues and adds the bio to delayed->list despite the fact that dc->may_delay is false. Fix this bug by changing may_delay's type from atomic_t to bool and only access it while holding the delayed_bios_lock mutex. Note that we don't have to grab the mutex in delay_resume because there are no bios in flight at this point. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer Signed-off-by: Sasha Levin --- drivers/md/dm-delay.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c index 59e51d285b0e5..238028056d0cc 100644 --- a/drivers/md/dm-delay.c +++ b/drivers/md/dm-delay.c @@ -30,7 +30,7 @@ struct delay_c { struct workqueue_struct *kdelayd_wq; struct work_struct flush_expired_bios; struct list_head delayed_bios; - atomic_t may_delay; + bool may_delay; struct delay_class read; struct delay_class write; @@ -191,7 +191,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); INIT_LIST_HEAD(&dc->delayed_bios); mutex_init(&dc->timer_lock); - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; dc->argc = argc; ret = delay_class_ctr(ti, &dc->read, argv); @@ -245,7 +245,7 @@ static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) struct dm_delay_info *delayed; unsigned long expires = 0; - if (!c->delay || !atomic_read(&dc->may_delay)) + if (!c->delay) return DM_MAPIO_REMAPPED; delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); @@ -254,6 +254,10 @@ static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay); mutex_lock(&delayed_bios_lock); + if (unlikely(!dc->may_delay)) { + mutex_unlock(&delayed_bios_lock); + return DM_MAPIO_REMAPPED; + } c->ops++; list_add_tail(&delayed->list, &dc->delayed_bios); mutex_unlock(&delayed_bios_lock); @@ -267,7 +271,10 @@ static void delay_presuspend(struct dm_target *ti) { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 0); + mutex_lock(&delayed_bios_lock); + dc->may_delay = false; + mutex_unlock(&delayed_bios_lock); + del_timer_sync(&dc->delay_timer); flush_bios(flush_delayed_bios(dc, 1)); } @@ -276,7 +283,7 @@ static void delay_resume(struct dm_target *ti) { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; } static int delay_map(struct dm_target *ti, struct bio *bio) -- 2.42.0