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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) {
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