Commit 7535b832 authored by Kees Cook's avatar Kees Cook
Browse files

exit: Use READ_ONCE() for all oops/warn limit reads 



Use a temporary variable to take full advantage of READ_ONCE() behavior.
Without this, the report (and even the test) might be out of sync with
the initial test.

Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/Y5x7GXeluFmZ8E0E@hirez.programming.kicks-ass.net


Fixes: 9fc9e278 ("panic: Introduce warn_limit")
Fixes: d4ccd54d ("exit: Put an upper limit on how often we can oops")
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jann Horn <jannh@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: tangmeng <tangmeng@uniontech.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent d6a9fb87

kernel/exit.c

+4 −2
Original line number Diff line number Diff line
@@ -931,6 +931,7 @@ void __noreturn make_task_dead(int signr) 
	 * Then do everything else.

	 */

	struct task_struct *tsk = current;

	unsigned int limit;



	if (unlikely(in_interrupt()))

		panic("Aiee, killing interrupt handler!");
@@ -954,8 +955,9 @@ void __noreturn make_task_dead(int signr) 
	 * To make sure this can't happen, place an upper bound on how often the

	 * kernel may oops without panic().

	 */

	if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit)

		panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit);

	limit = READ_ONCE(oops_limit);

	if (atomic_inc_return(&oops_count) >= limit && limit)

		panic("Oopsed too often (kernel.oops_limit is %d)", limit);



	/*

	 * We're taking recursive faults here in make_task_dead. Safest is to just

kernel/panic.c

+5 −2
Original line number Diff line number Diff line
@@ -231,12 +231,15 @@ static void panic_print_sys_info(bool console_flush) 


void check_panic_on_warn(const char *origin)

{

	unsigned int limit;



	if (panic_on_warn)

		panic("%s: panic_on_warn set ...\n", origin);



	if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit) && warn_limit)

	limit = READ_ONCE(warn_limit);

	if (atomic_inc_return(&warn_count) >= limit && limit)

		panic("%s: system warned too often (kernel.warn_limit is %d)",

		      origin, warn_limit);

		      origin, limit);

}



/**