This is a note to let you know that I've just added the patch titled

tracing: Fix crash when it fails to alloc ring buffer

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: tracing-fix-crash-when-it-fails-to-alloc-ring-buffer.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 24f2aaf952ee0b59f31c3a18b8b36c9e3d3c2cf5 Mon Sep 17 00:00:00 2001

From: Jing Xia jing.xia@spreadtrum.com Date: Tue, 26 Dec 2017 15:12:53 +0800 Subject: tracing: Fix crash when it fails to alloc ring buffer

From: Jing Xia jing.xia@spreadtrum.com

commit 24f2aaf952ee0b59f31c3a18b8b36c9e3d3c2cf5 upstream.

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

Link: http://lkml.kernel.org/r/20171226071253.8968-1-chunyan.zhang@spreadtrum.com

Fixes: 737223fbca3b1 ("tracing: Consolidate buffer allocation code") Signed-off-by: Jing Xia jing.xia@spreadtrum.com Signed-off-by: Chunyan Zhang chunyan.zhang@spreadtrum.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- kernel/trace/trace.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6268,7 +6268,9 @@ static int allocate_trace_buffers(struct 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;

Patches currently in stable-queue which might be from jing.xia@spreadtrum.com are

queue-3.18/tracing-fix-crash-when-it-fails-to-alloc-ring-buffer.patch queue-3.18/tracing-fix-possible-double-free-on-failure-of-allocating-trace-buffer.patch