linux-kernel - [PATCH 5.15 01/28] tick/nohz: unexport __init-annotated tick_nohz_full

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220630133232.972417691@linuxfoundation.org>
Date:   Thu, 30 Jun 2022 15:46:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Thomas Backlund <tmb@....nu>
Subject: [PATCH 5.15 01/28] tick/nohz: unexport __init-annotated tick_nohz_full_setup()

From: Masahiro Yamada <masahiroy@...nel.org>

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@...ux-foundation.org>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Tested-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Thomas Backlund <tmb@....nu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/time/tick-sched.c |    1 -
 1 file changed, 1 deletion(-)

--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -509,7 +509,6 @@ 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)
 {