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

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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: Peter 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: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kees Cook 2023-02-01 20:42:55 -08:00 committed by Greg Kroah-Hartman
parent eb768617da
commit a7cc1b5d76
2 changed files with 9 additions and 4 deletions
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6
kernel/exit.c
View File

@ -917,6 +917,7 @@ void __noreturn make_task_dead(int signr)
* Take the task off the cpu after something catastrophic has * Take the task off the cpu after something catastrophic has
* happened. * happened.
*/ */
unsigned int limit;
/* /*
* Every time the system oopses, if the oops happens while a reference * 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 * To make sure this can't happen, place an upper bound on how often the
* kernel may oops without panic(). * kernel may oops without panic().
*/ */
if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit) limit = READ_ONCE(oops_limit);
panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); if (atomic_inc_return(&oops_count) >= limit && limit)
panic("Oopsed too often (kernel.oops_limit is %d)", limit);
do_exit(signr); do_exit(signr);
} }

7
kernel/panic.c
View File

@ -199,12 +199,15 @@ static void panic_print_sys_info(void)
void check_panic_on_warn(const char *origin) void check_panic_on_warn(const char *origin)
{ {
unsigned int limit;
if (panic_on_warn) if (panic_on_warn)
panic("%s: panic_on_warn set ...\n", origin); 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)", panic("%s: system warned too often (kernel.warn_limit is %d)",
origin, warn_limit); origin, limit);
} }
/** /**