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Message-ID: <20171226112224.216191dc@gandalf.local.home> Date: Tue, 26 Dec 2017 11:22:24 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Chunyan Zhang <chunyan.zhang@...eadtrum.com> Cc: Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>, Jing Xia <jing.xia@...eadtrum.com>, Orson Zhai <orson.zhai@...eadtrum.com>, Chunyan Zhang <zhang.lyra@...il.com> Subject: Re: [PATCH] tracing: Fix crash when it fails to alloc ring buffer On Tue, 26 Dec 2017 15:12:53 +0800 Chunyan Zhang <chunyan.zhang@...eadtrum.com> wrote: > From: Jing Xia <jing.xia@...eadtrum.com> > > Double free of the ring buffer happens when it fails to alloc new > ring buffer instance for max_buffer if TRACER_MAX_TRACE is configured. > The root cause is that the pointer is not set to NULL after the buffer > is freed in allocate_trace_buffers(), and the freeing of the ring > buffer is invoked again later if the pointer is not equal to Null, > as: > > instance_mkdir() > |-allocate_trace_buffers() > |-allocate_trace_buffer(tr, &tr->trace_buffer...) > |-allocate_trace_buffer(tr, &tr->max_buffer...) > > // allocate fail(-ENOMEM),first free > // and the buffer pointer is not set to null > |-ring_buffer_free(tr->trace_buffer.buffer) > > // out_free_tr > |-free_trace_buffers() > |-free_trace_buffer(&tr->trace_buffer); > > //if trace_buffer is not null, free again > |-ring_buffer_free(buf->buffer) > |-rb_free_cpu_buffer(buffer->buffers[cpu]) > // ring_buffer_per_cpu is null, and > // crash in ring_buffer_per_cpu->pages > > Signed-off-by: Jing Xia <jing.xia@...eadtrum.com> > Signed-off-by: Chunyan Zhang <chunyan.zhang@...eadtrum.com> Thanks! I'll apply this to my tree and start testing it. -- Steve > --- > kernel/trace/trace.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 73e67b6..ed1c0d1 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -7622,7 +7622,9 @@ static int allocate_trace_buffers(struct trace_array *tr, int size) > allocate_snapshot ? size : 1); > if (WARN_ON(ret)) { > ring_buffer_free(tr->trace_buffer.buffer); > + tr->trace_buffer.buffer = NULL; > free_percpu(tr->trace_buffer.data); > + tr->trace_buffer.data = NULL; > return -ENOMEM; > } > tr->allocated_snapshot = allocate_snapshot;
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