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Steven Rostedt (Google) authored
On some machines the number of listed CPUs may be bigger than the actual CPUs that exist. The tracing subsystem allocates a per_cpu directory with access to the per CPU ring buffer via a cpuX file. But to save space, the ring buffer will only allocate buffers for online CPUs, even though the CPU array will be as big as the nr_cpu_ids. With the addition of waking waiters on the ring buffer when closing the file, the ring_buffer_wake_waiters() now needs to make sure that the buffer is allocated (with the irq_work allocated with it) before trying to wake waiters, as it will cause a NULL pointer dereference. While debugging this, I added a NULL check for the buffer itself (which is OK to do), and also NULL pointer checks against buffer->buffers (which is not fine, and will WARN) as well as making sure the CPU number passed in is within the nr_cpu_ids (which is also not fine if it isn't). Link: https://lore.kernel.org/all/87h6zklb6n.wl-tiwai@suse.de/ Link: https://lore.kernel.org/all/CAM6Wdxc0KRJMXVAA0Y=u6Jh2V=uWB-_Fn6M4xRuNppfXzL1mUg@mail.gmail.com/ Link: https://lkml.kernel.org/linux-trace-kernel/20221101191009.1e7378c8@rorschach.local.home Cc: stable@vger.kernel.org Cc: Steven Noonan <steven.noonan@gmail.com> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1204705Reported-by:
Takashi Iwai <tiwai@suse.de> Reported-by:
Roland Ruckerbauer <roland.rucky@gmail.com> Fixes: f3ddb74a ("tracing: Wake up ring buffer waiters on closing of the file") Reviewed-by:
Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by:
Steven Rostedt (Google) <rostedt@goodmis.org>
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