Commit 22b2beaa authored Nov 27, 2020 by Sai Prakash Ranjan Committed by Greg Kroah-Hartman Nov 27, 2020

coresight: etb10: Fix possible NULL ptr dereference in etb_enable_perf()



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().

Fixes: 75d7dbd3 ("coresight: etb10: Add support for CPU-wide trace scenarios")
Cc: stable@vger.kernel.org
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20201127175256.1092685-11-mathieu.poirier@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 868663dd

drivers/hwtracing/coresight/coresight-etb10.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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;