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 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
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-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 24f2aaf952ee0b59f31c3a18b8b36c9e3d3c2cf5 Mon Sep 17 00:00:00 2001
From: Jing Xia <jing.xia@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx
Fixes: 737223fbca3b1 ("tracing: Consolidate buffer allocation code")
Signed-off-by: Jing Xia <jing.xia@xxxxxxxxxxxxxx>
Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6555,7 +6555,9 @@ 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@xxxxxxxxxxxxxx are
queue-4.4/tracing-fix-crash-when-it-fails-to-alloc-ring-buffer.patch
queue-4.4/tracing-fix-possible-double-free-on-failure-of-allocating-trace-buffer.patch