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trace: Fix race in trace_open and buffer resize call

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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 infine loop in rb_remove_pages
and rb_insert_pages while checking pages for sanity.

Take ring buffer lock in rb reset to avoid resetting of cpu buffer.

Change-Id: I1d3344cca99e936d4e04a0e430e0ef9a975404c8
Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
This commit is contained in:
Gaurav Kohli 2020-09-03 13:12:25 +05:30 • committed by Shadab Naseem
parent 585c41639c
commit a3ec7ba0db
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/ring_buffer.c
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@ -4359,6 +4359,8 @@ 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);
@ -4382,6 +4384,8 @@ 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);