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 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 change as ETF where we cache PID in alloc_buffer() callback which is called as the part of etm_setup_aux(). This will reduce the task_pid_nr() function call overheads as well. In addition to this, add a check to validate event->owner before dereferencing it to fix any possible NULL pointer dereference crashes and check for kernel events.
Fixes: 75d7dbd38824 ("coresight: etb10: Add support for CPU-wide trace scenarios") Suggested-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org --- drivers/hwtracing/coresight/coresight-etb10.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 248cc82c838e..9d2f1ab0e29e 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; @@ -376,6 +377,10 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, { int node; struct cs_buffers *buf; + struct task_struct *task = READ_ONCE(event->owner); + + if (!task || is_kernel_event(event)) + return NULL;
node = (event->cpu == -1) ? NUMA_NO_NODE : cpu_to_node(event->cpu);
@@ -383,6 +388,7 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, if (!buf) return NULL;
+ buf->pid = task_pid_nr(task); buf->snapshot = overwrite; buf->nr_pages = nr_pages; buf->data_pages = pages;