Commit Message
Greg KH
Oct. 24, 2022, 11:30 a.m. UTC
From: Guilherme G. Piccoli <gpiccoli@igalia.com> [ Upstream commit 3e081438b8e639cc76ef1a5ce0c1bd8a154082c7 ] Currently the gsmi driver registers a panic notifier as well as reboot and die notifiers. The callbacks registered are called in atomic and very limited context - for instance, panic disables preemption and local IRQs, also all secondary CPUs (not executing the panic path) are shutdown. With that said, taking a spinlock in this scenario is a dangerous invitation for lockup scenarios. So, fix that by checking if the spinlock is free to acquire in the panic notifier callback - if not, bail-out and avoid a potential hang. Fixes: 74c5b31c6618 ("driver: Google EFI SMI") Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: David Gow <davidgow@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Julius Werner <jwerner@chromium.org> Cc: Petr Mladek <pmladek@suse.com> Reviewed-by: Evan Green <evgreen@chromium.org> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Link: https://lore.kernel.org/r/20220909200755.189679-1-gpiccoli@igalia.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/firmware/google/gsmi.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c index 62337be07afc..2e3ef0eb6e82 100644 --- a/drivers/firmware/google/gsmi.c +++ b/drivers/firmware/google/gsmi.c @@ -661,6 +661,15 @@ static struct notifier_block gsmi_die_notifier = { static int gsmi_panic_callback(struct notifier_block *nb, unsigned long reason, void *arg) { + + /* + * Panic callbacks are executed with all other CPUs stopped, + * so we must not attempt to spin waiting for gsmi_dev.lock + * to be released. + */ + if (spin_is_locked(&gsmi_dev.lock)) + return NOTIFY_DONE; + gsmi_shutdown_reason(GSMI_SHUTDOWN_PANIC); return NOTIFY_DONE; }