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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2014-06-10 09:46:00 -0400 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-07-18 15:51:30 +0200 |
| commit | ca846a7a1fa185cf2520a755ba1944efac9b75f7 (patch) | |
| tree | 9a0a939119ef3def2123abce0289ec2ccfcdadeb /kernel/trace/ring_buffer.c | |
| parent | 378005bbce5cbbadadd581a9edc7d960b4316560 (diff) | |
| download | lwn-ca846a7a1fa185cf2520a755ba1944efac9b75f7.tar.gz lwn-ca846a7a1fa185cf2520a755ba1944efac9b75f7.zip | |
ring-buffer: Check if buffer exists before polling
commit 8b8b36834d0fff67fc8668093f4312dd04dcf21d upstream.
The per_cpu buffers are created one per possible CPU. But these do
not mean that those CPUs are online, nor do they even exist.
With the addition of the ring buffer polling, it assumes that the
caller polls on an existing buffer. But this is not the case if
the user reads trace_pipe from a CPU that does not exist, and this
causes the kernel to crash.
Simple fix is to check the cpu against buffer bitmask against to see
if the buffer was allocated or not and return -ENODEV if it is
not.
More updates were done to pass the -ENODEV back up to userspace.
Link: http://lkml.kernel.org/r/5393DB61.6060707@oracle.com
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'kernel/trace/ring_buffer.c')
| -rw-r--r-- | kernel/trace/ring_buffer.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0e337eedb909..15c4ae203885 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -543,7 +543,7 @@ static void rb_wake_up_waiters(struct irq_work *work) * as data is added to any of the @buffer's cpu buffers. Otherwise * it will wait for data to be added to a specific cpu buffer. */ -void ring_buffer_wait(struct ring_buffer *buffer, int cpu) +int ring_buffer_wait(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; DEFINE_WAIT(wait); @@ -557,6 +557,8 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu) if (cpu == RING_BUFFER_ALL_CPUS) work = &buffer->irq_work; else { + if (!cpumask_test_cpu(cpu, buffer->cpumask)) + return -ENODEV; cpu_buffer = buffer->buffers[cpu]; work = &cpu_buffer->irq_work; } @@ -591,6 +593,7 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu) schedule(); finish_wait(&work->waiters, &wait); + return 0; } /** |