This is a note to let you know that I've just added the patch titled
ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI
to the 5.4-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:
ring-buffer-do-not-record-in-nmi-if-the-arch-does-no.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bf76a80555cff2b51a4ed37bbed5806514c52561
Author: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Date: Wed Dec 13 17:54:03 2023 -0500
ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI
[ Upstream commit 712292308af2265cd9b126aedfa987f10f452a33 ]
As the ring buffer recording requires cmpxchg() to work, if the
architecture does not support cmpxchg in NMI, then do not do any recording
within an NMI.
Link: https://lore.kernel.org/linux-trace-kernel/20231213175403.6fc18540@xxxxxxxxxxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 4a03eac43aaf..0c0ca21d807d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2976,6 +2976,12 @@ rb_reserve_next_event(struct ring_buffer *buffer,
int nr_loops = 0;
u64 diff;
+ /* ring buffer does cmpxchg, make sure it is safe in NMI context */
+ if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
+ (unlikely(in_nmi()))) {
+ return NULL;
+ }
+
rb_start_commit(cpu_buffer);
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
