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 D6B98847A for ; Wed, 1 Mar 2023 18:11:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61BB6C433D2; Wed, 1 Mar 2023 18:11:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1677694274; bh=B+lJ34fJtr6JYae+SXPoMmqz5fHA87kogxqn90Yo0fw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WIYUkVYv710E7bLPUkgPUXU+FfraC3i8uKzjDYWZMXGh+c8n+ZbAgDerpPB5iBemy ZGHJ4pUAZ6PkdEYjsDGepOme6C16uSaIP5YHnwpNVrTyBcHNy3xaN8ZwsdyF5/Z2nb dlO5ZidT2a/9m3xywS5+wWdPQODuhZTglOHfZTL8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dan Williams , Vishal Verma , Sasha Levin Subject: [PATCH 5.15 06/22] ACPI: NFIT: fix a potential deadlock during NFIT teardown Date: Wed, 1 Mar 2023 19:08:39 +0100 Message-Id: <20230301180652.918994976@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230301180652.658125575@linuxfoundation.org> References: <20230301180652.658125575@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Vishal Verma [ Upstream commit fb6df4366f86dd252bfa3049edffa52d17e7b895 ] Lockdep reports that acpi_nfit_shutdown() may deadlock against an opportune acpi_nfit_scrub(). acpi_nfit_scrub () is run from inside a 'work' and therefore has already acquired workqueue-internal locks. It also acquiires acpi_desc->init_mutex. acpi_nfit_shutdown() first acquires init_mutex, and was subsequently attempting to cancel any pending workqueue items. This reversed locking order causes a potential deadlock: ====================================================== WARNING: possible circular locking dependency detected 6.2.0-rc3 #116 Tainted: G O N ------------------------------------------------------ libndctl/1958 is trying to acquire lock: ffff888129b461c0 ((work_completion)(&(&acpi_desc->dwork)->work)){+.+.}-{0:0}, at: __flush_work+0x43/0x450 but task is already holding lock: ffff888129b460e8 (&acpi_desc->init_mutex){+.+.}-{3:3}, at: acpi_nfit_shutdown+0x87/0xd0 [nfit] which lock already depends on the new lock. ... Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&acpi_desc->init_mutex); lock((work_completion)(&(&acpi_desc->dwork)->work)); lock(&acpi_desc->init_mutex); lock((work_completion)(&(&acpi_desc->dwork)->work)); *** DEADLOCK *** Since the workqueue manipulation is protected by its own internal locking, the cancellation of pending work doesn't need to be done under acpi_desc->init_mutex. Move cancel_delayed_work_sync() outside the init_mutex to fix the deadlock. Any work that starts after acpi_nfit_shutdown() drops the lock will see ARS_CANCEL, and the cancel_delayed_work_sync() will safely flush it out. Reported-by: Dan Williams Signed-off-by: Vishal Verma Link: https://lore.kernel.org/r/20230112-acpi_nfit_lockdep-v1-1-660be4dd10be@intel.com Signed-off-by: Dan Williams Signed-off-by: Sasha Levin --- drivers/acpi/nfit/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c index 7dd80acf92c78..2575d6c51f898 100644 --- a/drivers/acpi/nfit/core.c +++ b/drivers/acpi/nfit/core.c @@ -3676,8 +3676,8 @@ void acpi_nfit_shutdown(void *data) mutex_lock(&acpi_desc->init_mutex); set_bit(ARS_CANCEL, &acpi_desc->scrub_flags); - cancel_delayed_work_sync(&acpi_desc->dwork); mutex_unlock(&acpi_desc->init_mutex); + cancel_delayed_work_sync(&acpi_desc->dwork); /* * Bounce the nvdimm bus lock to make sure any in-flight -- 2.39.0