This is a note to let you know that I've just added the patch titled
tick/nohz: unexport __init-annotated tick_nohz_full_setup()
to the 5.10-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:
tick-nohz-unexport-__init-annotated-tick_nohz_full_setup.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2390095113e98fc52fffe35c5206d30d9efe3f78 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date: Mon, 27 Jun 2022 12:22:09 +0900
Subject: tick/nohz: unexport __init-annotated tick_nohz_full_setup()
From: Masahiro Yamada <masahiroy@xxxxxxxxxx>
commit 2390095113e98fc52fffe35c5206d30d9efe3f78 upstream.
EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.
modpost used to detect it, but it had been broken for a decade.
Commit 28438794aba4 ("modpost: fix section mismatch check for exported
init/exit sections") fixed it so modpost started to warn it again, then
this showed up:
MODPOST vmlinux.symvers
WARNING: modpost: vmlinux.o(___ksymtab_gpl+tick_nohz_full_setup+0x0): Section mismatch in reference from the variable __ksymtab_tick_nohz_full_setup to the function .init.text:tick_nohz_full_setup()
The symbol tick_nohz_full_setup is exported and annotated __init
Fix this by removing the __init annotation of tick_nohz_full_setup or drop the export.
Drop the export because tick_nohz_full_setup() is only called from the
built-in code in kernel/sched/isolation.c.
Fixes: ae9e557b5be2 ("time: Export tick start/stop functions for rcutorture")
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Backlund <tmb@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/tick-sched.c | 1 -
1 file changed, 1 deletion(-)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -425,7 +425,6 @@ void __init tick_nohz_full_setup(cpumask
cpumask_copy(tick_nohz_full_mask, cpumask);
tick_nohz_full_running = true;
}
-EXPORT_SYMBOL_GPL(tick_nohz_full_setup);
static int tick_nohz_cpu_down(unsigned int cpu)
{
Patches currently in stable-queue which might be from masahiroy@xxxxxxxxxx are
queue-5.10/tick-nohz-unexport-__init-annotated-tick_nohz_full_setup.patch
