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Thu, 22 Oct 2020 10:58:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 7BA18C43387 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=saiprakash.ranjan@codeaurora.org From: Sai Prakash Ranjan To: Mathieu Poirier , Suzuki K Poulose , Mike Leach , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim Subject: [PATCHv2 4/4] coresight: tmc-etr: Fix possible NULL ptr dereference in get_perf_etr_buf_cpu_wide() Date: Thu, 22 Oct 2020 16:27:54 +0530 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201022_065842_984138_C748C2BC X-CRM114-Status: GOOD ( 17.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sai Prakash Ranjan , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org There was a report of NULL pointer dereference in ETF enable path for perf CS mode with PID monitoring. It is almost 100% reproducible when the process to monitor is something very active such as chrome and with ETF as the sink but the ETR may also be susceptible to this crash. Currently in a bid to find the pid, the owner is dereferenced via task_pid_nr() call in get_perf_etr_buf_cpu_wide() and with owner being NULL and no proper validation of event->owner, we can have a possible NULL pointer dereference, so add a check to validate event->owner before dereferencing it to fix any possible NULL pointer dereference crashes and also check for kernel events. Fixes: 3147da92a8a8 ("coresight: tmc-etr: Allocate and free ETR memory buffers for CPU-wide scenarios") Suggested-by: Suzuki K Poulose Signed-off-by: Sai Prakash Ranjan --- drivers/hwtracing/coresight/coresight-tmc-etr.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 714f9e867e5f..305dfdd5345a 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1381,6 +1381,10 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev, { struct etr_perf_buffer *etr_perf; struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); + struct task_struct *task = READ_ONCE(event->owner); + + if (!task || is_kernel_event(event)) + return NULL; etr_perf = tmc_etr_setup_perf_buf(drvdata, event, nr_pages, pages, snapshot); @@ -1389,7 +1393,7 @@ static void *tmc_alloc_etr_buffer(struct coresight_device *csdev, return NULL; } - etr_perf->pid = task_pid_nr(event->owner); + etr_perf->pid = task_pid_nr(task); etr_perf->snapshot = snapshot; etr_perf->nr_pages = nr_pages; etr_perf->pages = pages;