This is a note to let you know that I've just added the patch titled
ring-buffer: Have rb_time_cmpxchg() set the msb counter too
to the 6.6-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-have-rb_time_cmpxchg-set-the-msb-counter-too.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0aa0e5289cfe984a8a9fdd79ccf46ccf080151f7 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Fri, 15 Dec 2023 08:41:14 -0500
Subject: ring-buffer: Have rb_time_cmpxchg() set the msb counter too
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
commit 0aa0e5289cfe984a8a9fdd79ccf46ccf080151f7 upstream.
The rb_time_cmpxchg() on 32-bit architectures requires setting three
32-bit words to represent the 64-bit timestamp, with some salt for
synchronization. Those are: msb, top, and bottom
The issue is, the rb_time_cmpxchg() did not properly salt the msb portion,
and the msb that was written was stale.
Link: https://lore.kernel.org/linux-trace-kernel/20231215084114.20899342@xxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Fixes: f03f2abce4f39 ("ring-buffer: Have 32 bit time stamps use all 64 bits")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/ring_buffer.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -722,10 +722,12 @@ static bool rb_time_cmpxchg(rb_time_t *t
cnt2 = cnt + 1;
rb_time_split(val, &top, &bottom, &msb);
+ msb = rb_time_val_cnt(msb, cnt);
top = rb_time_val_cnt(top, cnt);
bottom = rb_time_val_cnt(bottom, cnt);
rb_time_split(set, &top2, &bottom2, &msb2);
+ msb2 = rb_time_val_cnt(msb2, cnt);
top2 = rb_time_val_cnt(top2, cnt2);
bottom2 = rb_time_val_cnt(bottom2, cnt2);
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-6.6/ring-buffer-do-not-update-before-stamp-when-switching-sub-buffers.patch
queue-6.6/ring-buffer-have-saved-event-hold-the-entire-event.patch
queue-6.6/eventfs-do-not-allow-null-parent-to-eventfs_start_cr.patch
queue-6.6/ring-buffer-have-rb_time_cmpxchg-set-the-msb-counter-too.patch
queue-6.6/ring-buffer-do-not-try-to-put-back-write_stamp.patch
queue-6.6/ring-buffer-fix-memory-leak-of-free-page.patch
queue-6.6/ring-buffer-fix-a-race-in-rb_time_cmpxchg-for-32-bit-archs.patch
queue-6.6/tracing-update-snapshot-buffer-on-resize-if-it-is-allocated.patch
queue-6.6/ring-buffer-fix-writing-to-the-buffer-with-max_data_size.patch
