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Commit a7cc1b5d authored by Kees Cook's avatar Kees Cook Committed by Greg Kroah-Hartman
Browse files

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



commit 7535b832c6399b5ebfc5b53af5c51dd915ee2538 upstream.

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: 9fc9e278a5c0 ("panic: Introduce warn_limit")
Fixes: d4ccd54d28d3 ("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>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent eb768617

kernel/exit.c

+4 −2
Original line number Diff line number Diff line
@@ -917,6 +917,7 @@ void __noreturn make_task_dead(int signr) 
	 * Take the task off the cpu after something catastrophic has

	 * happened.

	 */

	unsigned int limit;



	/*

	 * Every time the system oopses, if the oops happens while a reference
@@ -928,8 +929,9 @@ 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);



	do_exit(signr);

}

kernel/panic.c

+5 −2
Original line number Diff line number Diff line
@@ -199,12 +199,15 @@ static void panic_print_sys_info(void) 


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);

}



/**