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authorGuilherme G. Piccoli <gpiccoli@igalia.com>2022-09-09 17:07:55 -0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-09-24 14:59:44 +0200
commit3e081438b8e639cc76ef1a5ce0c1bd8a154082c7 (patch)
tree5ea113fbc98d460da5135f911d9c3a9ad8750ab2 /drivers/firmware/google
parenta5ccec12acfaf3a7ebbbeb90555b35b275fce0df (diff)
firmware: google: Test spinlock on panic path to avoid lockups
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>
Diffstat (limited to 'drivers/firmware/google')
-rw-r--r--drivers/firmware/google/gsmi.c9
1 files changed, 9 insertions, 0 deletions
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;
}