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tracing: Fix race in trace_open and buffer resize call 

commit bbeb97464e upstream.

Below race can come, if trace_open and resize of
cpu buffer is running parallely on different cpus
CPUX                                CPUY
				    ring_buffer_resize
				    atomic_read(&buffer->resize_disabled)
tracing_open
tracing_reset_online_cpus
ring_buffer_reset_cpu
rb_reset_cpu
				    rb_update_pages
				    remove/insert pages
resetting pointer

This race can cause data abort or some times infinte loop in
rb_remove_pages and rb_insert_pages while checking pages
for sanity.

Take buffer lock to fix this.

Link: https://lkml.kernel.org/r/1601976833-24377-1-git-send-email-gkohli@codeaurora.org

Cc: stable@vger.kernel.org
Fixes: 83f40318da ("ring-buffer: Make removal of ring buffer pages atomic")
Reported-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Gaurav Kohli 2020-10-06 15:03:53 +05:30 committed by Greg Kroah-Hartman
parent c4a23c852e
commit b899d5b2a4
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/ring_buffer.c
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@ -4448,6 +4448,8 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
atomic_inc(&buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
@ -4471,6 +4473,8 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
atomic_dec(&cpu_buffer->record_disabled);
atomic_dec(&buffer->resize_disabled);
mutex_unlock(&buffer->mutex);
}
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);