From d576893936c6f8b34c4dc44aea3be8984ef7d8d0 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 20 Jan 2025 18:56:56 -0500 Subject: [PATCH] ring-buffer: Do not allow events in NMI with generic atomic64 cmpxchg() BugLink: https://bugs.launchpad.net/bugs/2114239 commit cd2375a3567fd3d93aa6c68e0027a5756213bda0 upstream. Some architectures can not safely do atomic64 operations in NMI context. Since the ring buffer relies on atomic64 operations to do its time keeping, if an event is requested in NMI context, reject it for these architectures. Cc: stable@vger.kernel.org Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Linus Torvalds Cc: Andreas Larsson Link: https://lore.kernel.org/20250120235721.407068250@goodmis.org Fixes: c84897c0ff592 ("ring-buffer: Remove 32bit timestamp logic") Closes: https://lore.kernel.org/all/86fb4f86-a0e4-45a2-a2df-3154acc4f086@gaisler.com/ Reported-by: Ludwig Rydberg Reviewed-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman Signed-off-by: Noah Wager Signed-off-by: Mehmet Basaran --- kernel/trace/ring_buffer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 65bfa671a1fc..9ebcf11b9d67 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3711,8 +3711,13 @@ rb_reserve_next_event(struct trace_buffer *buffer, int nr_loops = 0; int add_ts_default; - /* ring buffer does cmpxchg, make sure it is safe in NMI context */ - if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && + /* + * ring buffer does cmpxchg as well as atomic64 operations + * (which some archs use locking for atomic64), make sure this + * is safe in NMI context + */ + if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) || + IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) && (unlikely(in_nmi()))) { return NULL; }