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[68.147.0.187]) by smtp.gmail.com with ESMTPSA id t18sm10536724pji.1.2020.11.27.09.53.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Nov 2020 09:53:07 -0800 (PST) From: Mathieu Poirier To: gregkh@linuxfoundation.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 10/15] coresight: etb10: Fix possible NULL ptr dereference in etb_enable_perf() Date: Fri, 27 Nov 2020 10:52:51 -0700 Message-Id: <20201127175256.1092685-11-mathieu.poirier@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201127175256.1092685-1-mathieu.poirier@linaro.org> References: <20201127175256.1092685-1-mathieu.poirier@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sai Prakash Ranjan 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, not ETR. But code path shows that ETB has a similar path as ETF, so there could be possible NULL pointer dereference crash in ETB as well. Currently in a bid to find the pid, the owner is dereferenced via task_pid_nr() call in etb_enable_perf() and with owner being NULL, we can get a NULL pointer dereference, so have a similar fix as ETF where we cache PID in alloc_buffer() callback which is called as the part of etm_setup_aux(). Cc: stable@vger.kernel.org Fixes: 75d7dbd38824 ("coresight: etb10: Add support for CPU-wide trace scenarios") Signed-off-by: Sai Prakash Ranjan Signed-off-by: Mathieu Poirier --- drivers/hwtracing/coresight/coresight-etb10.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 248cc82c838e..1b320ab581ca 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -176,6 +176,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) unsigned long flags; struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); struct perf_output_handle *handle = data; + struct cs_buffers *buf = etm_perf_sink_config(handle); spin_lock_irqsave(&drvdata->spinlock, flags); @@ -186,7 +187,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) } /* Get a handle on the pid of the process to monitor */ - pid = task_pid_nr(handle->event->owner); + pid = buf->pid; if (drvdata->pid != -1 && drvdata->pid != pid) { ret = -EBUSY; @@ -383,6 +384,7 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, if (!buf) return NULL; + buf->pid = task_pid_nr(event->owner); buf->snapshot = overwrite; buf->nr_pages = nr_pages; buf->data_pages = pages; -- 2.25.1