From: Gaurav Kohli Date: Tue, 6 Oct 2020 09:33:53 +0000 (+0530) Subject: tracing: Fix race in trace_open and buffer resize call X-Git-Tag: v4.4.254~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a7c2dd4438056fb665a376860242463a30f2d2e8;p=thirdparty%2Fkernel%2Fstable.git tracing: Fix race in trace_open and buffer resize call commit bbeb97464eefc65f506084fd9f18f21653e01137 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: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic") Reported-by: Denis Efremov Signed-off-by: Gaurav Kohli Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 547a3a5ac57b5..1ec760f6bf58b 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4294,6 +4294,8 @@ 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); @@ -4317,6 +4319,8 @@ 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);