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 57E7C20E0 for ; Thu, 7 Apr 2022 01:14:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C834C385A7; Thu, 7 Apr 2022 01:14:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649294044; bh=DhR6AeTKiLjq/3nWP2sq4FthZdkWvOrag8B25MAR0RQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fUCtzrAMYtZ+GnJlKGukzTrjxKHssmlOLfAGwsG+DqyIlIAtL9zRIhKRDxaW2lqtV fSt4n5BYGZ3geRqdk2ZC0NJyi+hQmF9N33UXPbJbg71yfISVUUaNtJlwiKOPUuj3oS yvaXcHxUlnfdr0rGDG7y89NIaP19MRjV8T2nFBGkE2zC7qEtCIeprAXuUZgKS9QKu8 CIIxve9CtHtOlpYb6x4Vj+qHDpPe2dd0wQBQco+/dMbegRTR2H3AfTmQCDnrsizl2P +Ae3c8a+aMwk+O3vno4Wfsh6yB1mcfHmvpFViU2hQBCmeXJmmc9V7bTDrsFAy14Uup nNNlDBJOFvJhQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tzung-Bi Shih , Guenter Roeck , Benson Leung , Sasha Levin , chrome-platform@lists.linux.dev Subject: [PATCH AUTOSEL 5.15 24/27] platform/chrome: cros_ec_debugfs: detach log reader wq from devm Date: Wed, 6 Apr 2022 21:12:54 -0400 Message-Id: <20220407011257.114287-24-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220407011257.114287-1-sashal@kernel.org> References: <20220407011257.114287-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: chrome-platform@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Tzung-Bi Shih [ Upstream commit 0e8eb5e8acbad19ac2e1856b2fb2320184299b33 ] Debugfs console_log uses devm memory (e.g. debug_info in cros_ec_console_log_poll()). However, lifecycles of device and debugfs are independent. An use-after-free issue is observed if userland program operates the debugfs after the memory has been freed. The call trace: do_raw_spin_lock _raw_spin_lock_irqsave remove_wait_queue ep_unregister_pollwait ep_remove do_epoll_ctl A Python example to reproduce the issue: ... import select ... p = select.epoll() ... f = open('/sys/kernel/debug/cros_scp/console_log') ... p.register(f, select.POLLIN) ... p.poll(1) [(4, 1)] # 4=fd, 1=select.POLLIN [ shutdown cros_scp at the point ] ... p.poll(1) [(4, 16)] # 4=fd, 16=select.POLLHUP ... p.unregister(f) An use-after-free issue raises here. It called epoll_ctl with EPOLL_CTL_DEL which in turn to use the workqueue in the devm (i.e. log_wq). Detaches log reader's workqueue from devm to make sure it is persistent even if the device has been removed. Signed-off-by: Tzung-Bi Shih Reviewed-by: Guenter Roeck Link: https://lore.kernel.org/r/20220209051130.386175-1-tzungbi@google.com Signed-off-by: Benson Leung Signed-off-by: Sasha Levin --- drivers/platform/chrome/cros_ec_debugfs.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c index 272c89837d74..0dbceee87a4b 100644 --- a/drivers/platform/chrome/cros_ec_debugfs.c +++ b/drivers/platform/chrome/cros_ec_debugfs.c @@ -25,6 +25,9 @@ #define CIRC_ADD(idx, size, value) (((idx) + (value)) & ((size) - 1)) +/* waitqueue for log readers */ +static DECLARE_WAIT_QUEUE_HEAD(cros_ec_debugfs_log_wq); + /** * struct cros_ec_debugfs - EC debugging information. * @@ -33,7 +36,6 @@ * @log_buffer: circular buffer for console log information * @read_msg: preallocated EC command and buffer to read console log * @log_mutex: mutex to protect circular buffer - * @log_wq: waitqueue for log readers * @log_poll_work: recurring task to poll EC for new console log data * @panicinfo_blob: panicinfo debugfs blob */ @@ -44,7 +46,6 @@ struct cros_ec_debugfs { struct circ_buf log_buffer; struct cros_ec_command *read_msg; struct mutex log_mutex; - wait_queue_head_t log_wq; struct delayed_work log_poll_work; /* EC panicinfo */ struct debugfs_blob_wrapper panicinfo_blob; @@ -107,7 +108,7 @@ static void cros_ec_console_log_work(struct work_struct *__work) buf_space--; } - wake_up(&debug_info->log_wq); + wake_up(&cros_ec_debugfs_log_wq); } mutex_unlock(&debug_info->log_mutex); @@ -141,7 +142,7 @@ static ssize_t cros_ec_console_log_read(struct file *file, char __user *buf, mutex_unlock(&debug_info->log_mutex); - ret = wait_event_interruptible(debug_info->log_wq, + ret = wait_event_interruptible(cros_ec_debugfs_log_wq, CIRC_CNT(cb->head, cb->tail, LOG_SIZE)); if (ret < 0) return ret; @@ -173,7 +174,7 @@ static __poll_t cros_ec_console_log_poll(struct file *file, struct cros_ec_debugfs *debug_info = file->private_data; __poll_t mask = 0; - poll_wait(file, &debug_info->log_wq, wait); + poll_wait(file, &cros_ec_debugfs_log_wq, wait); mutex_lock(&debug_info->log_mutex); if (CIRC_CNT(debug_info->log_buffer.head, @@ -377,7 +378,6 @@ static int cros_ec_create_console_log(struct cros_ec_debugfs *debug_info) debug_info->log_buffer.tail = 0; mutex_init(&debug_info->log_mutex); - init_waitqueue_head(&debug_info->log_wq); debugfs_create_file("console_log", S_IFREG | 0444, debug_info->dir, debug_info, &cros_ec_console_log_fops); -- 2.35.1