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authorSteven Rostedt (Google) <rostedt@goodmis.org>2022-11-01 19:10:09 -0400
committerSteven Rostedt (Google) <rostedt@goodmis.org>2022-11-02 23:52:03 -0400
commit7433632c9ff68a991bd0bc38cabf354e9d2de410 (patch)
treee93e44ebf9448a608d89694d89cb3e7e4e78c9b5 /kernel
parent30a0b95b1335e12efef89dd78518ed3e4a71a763 (diff)
ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters()
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=1204705 Reported-by: Takashi Iwai <tiwai@suse.de> Reported-by: Roland Ruckerbauer <roland.rucky@gmail.com> Fixes: f3ddb74ad079 ("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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ring_buffer.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 199759c73519..9712083832f4 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -937,6 +937,9 @@ void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
struct ring_buffer_per_cpu *cpu_buffer;
struct rb_irq_work *rbwork;
+ if (!buffer)
+ return;
+
if (cpu == RING_BUFFER_ALL_CPUS) {
/* Wake up individual ones too. One level recursion */
@@ -945,7 +948,15 @@ void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
rbwork = &buffer->irq_work;
} else {
+ if (WARN_ON_ONCE(!buffer->buffers))
+ return;
+ if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
+ return;
+
cpu_buffer = buffer->buffers[cpu];
+ /* The CPU buffer may not have been initialized yet */
+ if (!cpu_buffer)
+ return;
rbwork = &cpu_buffer->irq_work;
}