| Message ID | 20220909200755.189679-1-gpiccoli@igalia.com |
|---|---|
| State | Accepted |
| Commit | 3e081438b8e639cc76ef1a5ce0c1bd8a154082c7 |
| Headers | show |
| Series | [V4] firmware: google: Test spinlock on panic path to avoid lockups | expand |
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; }
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> --- Hey folks, new version - V3 available at [0]. @Greg, I think the panic situation is well-described in the commit message so I didn't rework that, lemme know if you want to add something to the text. @Evan, I kept your review tag even with the comment change, based on the V3 discussion. Lemme know if you want it removed in case you disagree with something! V4: * Reworked comment (thanks Andrew, for the suggestion!); * Rebased against 6.0-rc4; * Included more CCs (Andrew, Petr). [0] https://lore.kernel.org/linux-kernel/20220819155059.451674-1-gpiccoli@igalia.com/ drivers/firmware/google/gsmi.c | 9 +++++++++ 1 file changed, 9 insertions(+)