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 adaa492c3d2d..4e2575dfeb90 100644 --- a/drivers/firmware/google/gsmi.c +++ b/drivers/firmware/google/gsmi.c @@ -681,6 +681,15 @@ 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; }