From: Kees Cook keescook@chromium.org
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.ne... 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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/exit.c | 6 ++++-- kernel/panic.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-)
--- a/kernel/exit.c +++ b/kernel/exit.c @@ -973,6 +973,7 @@ 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 @@ -984,8 +985,9 @@ 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); } --- a/kernel/panic.c +++ b/kernel/panic.c @@ -165,12 +165,15 @@ EXPORT_SYMBOL(nmi_panic);
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); }
/**