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Date: Wed, 1 Feb 2023 20:42:55 -0800 From: Eric Biggers <ebiggers@...nel.org> To: stable@...r.kernel.org Cc: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>, Kees Cook <keescook@...omium.org>, SeongJae Park <sj@...nel.org>, Seth Jenkins <sethjenkins@...gle.com>, Jann Horn <jannh@...gle.com>, "Eric W . Biederman" <ebiederm@...ssion.com>, linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, Petr Mladek <pmladek@...e.com>, Andrew Morton <akpm@...ux-foundation.org>, Luis Chamberlain <mcgrof@...nel.org>, Marco Elver <elver@...gle.com>, tangmeng <tangmeng@...ontech.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Tiezhu Yang <yangtiezhu@...ngson.cn>, Peter Zijlstra <peterz@...radead.org> Subject: [PATCH 5.4 17/17] exit: Use READ_ONCE() for all oops/warn limit reads From: Kees Cook <keescook@...omium.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@...radead.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@...ssion.com> Cc: Jann Horn <jannh@...gle.com> Cc: Arnd Bergmann <arnd@...db.de> Cc: Petr Mladek <pmladek@...e.com> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Luis Chamberlain <mcgrof@...nel.org> Cc: Marco Elver <elver@...gle.com> Cc: tangmeng <tangmeng@...ontech.com> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de> Cc: Tiezhu Yang <yangtiezhu@...ngson.cn> Signed-off-by: Kees Cook <keescook@...omium.org> Signed-off-by: Eric Biggers <ebiggers@...gle.com> --- kernel/exit.c | 6 ++++-- kernel/panic.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 381282fb756c3..563bdaa766945 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -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); } diff --git a/kernel/panic.c b/kernel/panic.c index 2c118645e7408..cef79466f9417 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -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); } /** -- 2.39.1
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