From: Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxxxxxx> Link: https://lore.kernel.org/lkml/Y5x7GXeluFmZ8E0E@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 9fc9e278a5c0 ("panic: Introduce warn_limit") Fixes: d4ccd54d28d3 ("exit: Put an upper limit on how often we can oops") Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Petr Mladek <pmladek@xxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: tangmeng <tangmeng@xxxxxxxxxxxxx> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/exit.c | 6 ++++-- kernel/panic.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-) --- a/kernel/exit.c +++ b/kernel/exit.c @@ -975,6 +975,7 @@ 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 @@ -986,8 +987,9 @@ 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 @@ -168,12 +168,15 @@ 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); } /**
