From: Lai Jiangshan Date: Mon, 8 Mar 2010 06:50:43 +0000 (+0800) Subject: ring-buffer: Move disabled check into preempt disable section X-Git-Tag: firefly_0821_release~10186^2~2016 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=9dfa691caee866df28691815e708a914349a6f10;p=firefly-linux-kernel-4.4.55.git ring-buffer: Move disabled check into preempt disable section commit 52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4 upstream. The ring buffer resizing and resetting relies on a schedule RCU action. The buffers are disabled, a synchronize_sched() is called and then the resize or reset takes place. But this only works if the disabling of the buffers are within the preempt disabled section, otherwise a window exists that the buffers can be written to while a reset or resize takes place. Reported-by: Li Zefan Signed-off-by: Lai Jiangshan LKML-Reference: <4B949E43.2010906@cn.fujitsu.com> Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 5dd017fea6f5..c88b21c9fb64 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2237,12 +2237,12 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) if (ring_buffer_flags != RB_BUFFERS_ON) return NULL; - if (atomic_read(&buffer->record_disabled)) - return NULL; - /* If we are tracing schedule, we don't want to recurse */ resched = ftrace_preempt_disable(); + if (atomic_read(&buffer->record_disabled)) + goto out_nocheck; + if (trace_recursive_lock()) goto out_nocheck; @@ -2474,11 +2474,11 @@ int ring_buffer_write(struct ring_buffer *buffer, if (ring_buffer_flags != RB_BUFFERS_ON) return -EBUSY; - if (atomic_read(&buffer->record_disabled)) - return -EBUSY; - resched = ftrace_preempt_disable(); + if (atomic_read(&buffer->record_disabled)) + goto out; + cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask))