linux-kernel - [PATCH ftrace/core 1/2] [BUGFIX] ftrace: Avoid panic when allocation of max

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Date:	Tue, 03 Jun 2014 13:28:03 +0900
From:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
To:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Cc:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ingo Molnar <mingo@...hat.com>, yrl.pp-manager.tt@...achi.com
Subject: [PATCH ftrace/core 1/2] [BUGFIX] ftrace: Avoid panic when
 allocation of max_buffer is failed

When allocation of max_buffer is failed, the kernel frees tr->trace_buffer.data
per CPU and return -ENOMEM in allocate_trace_buffers(). However,
tracer_alloc_buffers() calling allocate_trace_buffers() also frees the data
per CPU for -ENOMEM by allocate_trace_buffers(). Therefore, the allocation
failure induces double free.

For the out_free_mask path in tracer_alloc_buffers(),
global_trace.trace_buffer.data and global_trace.max_buffer.data are
not allocated yet, so free_percpu of those are not needed.

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org
---
 kernel/trace/trace.c |    4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 626dbfd..135af32 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6671,10 +6671,6 @@ __init static int tracer_alloc_buffers(void)
 out_free_temp_buffer:
 	ring_buffer_free(temp_buffer);
 out_free_cpumask:
-	free_percpu(global_trace.trace_buffer.data);
-#ifdef CONFIG_TRACER_MAX_TRACE
-	free_percpu(global_trace.max_buffer.data);
-#endif
 	free_cpumask_var(global_trace.tracing_cpumask);
 out_free_buffer_mask:
 	free_cpumask_var(tracing_buffer_mask);

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