This is a note to let you know that I've just added the patch titled
ring-buffer: Clean ring_buffer_poll_wait() error return
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-clean-ring_buffer_poll_wait-error-return.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.
>From 66bbea9ed6446b8471d365a22734dc00556c4785 Mon Sep 17 00:00:00 2001
From: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
Date: Wed, 31 Jan 2024 14:09:55 +0000
Subject: ring-buffer: Clean ring_buffer_poll_wait() error return
From: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
commit 66bbea9ed6446b8471d365a22734dc00556c4785 upstream.
The return type for ring_buffer_poll_wait() is __poll_t. This is behind
the scenes an unsigned where we can set event bits. In case of a
non-allocated CPU, we do return instead -EINVAL (0xffffffea). Lucky us,
this ends up setting few error bits (EPOLLERR | EPOLLHUP | EPOLLNVAL), so
user-space at least is aware something went wrong.
Nonetheless, this is an incorrect code. Replace that -EINVAL with a
proper EPOLLERR to clean that output. As this doesn't change the
behaviour, there's no need to treat this change as a bug fix.
Link: https://lore.kernel.org/linux-trace-kernel/20240131140955.3322792-1-vdonnefort@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 6721cb6002262 ("ring-buffer: Do not poll non allocated cpu buffers")
Signed-off-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
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, 1 insertion(+), 1 deletion(-)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -738,7 +738,7 @@ __poll_t ring_buffer_poll_wait(struct ri
full = 0;
} else {
if (!cpumask_test_cpu(cpu, buffer->cpumask))
- return -EINVAL;
+ return EPOLLERR;
cpu_buffer = buffer->buffers[cpu];
work = &cpu_buffer->irq_work;
Patches currently in stable-queue which might be from vdonnefort@xxxxxxxxxx are
queue-5.4/tracing-fix-wasted-memory-in-saved_cmdlines-logic.patch
queue-5.4/ring-buffer-clean-ring_buffer_poll_wait-error-return.patch
queue-5.4/tracing-trigger-fix-to-return-error-if-failed-to-alloc-snapshot.patch
