Commit ab8b9fd3 authored by Ashish Kalra's avatar Ashish Kalra Committed by Herbert Xu
Browse files

crypto: ccp - Fix SNP panic notifier unregistration 



Panic notifiers are invoked with RCU read lock held and when the
SNP panic notifier tries to unregister itself from the panic
notifier callback itself it causes a deadlock as notifier
unregistration does RCU synchronization.

Code flow for SNP panic notifier:
snp_shutdown_on_panic() ->
__sev_firmware_shutdown() ->
__sev_snp_shutdown_locked() ->
atomic_notifier_chain_unregister(.., &snp_panic_notifier)

Fix SNP panic notifier to unregister itself during SNP shutdown
only if panic is not in progress.

Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Fixes: 19860c32 ("crypto: ccp - Register SNP panic notifier only if SNP is enabled")
Signed-off-by: default avatarAshish Kalra <ashish.kalra@amd.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent f5ad93ff

drivers/crypto/ccp/sev-dev.c

+8 −2
Original line number Diff line number Diff line
@@ -1787,6 +1787,12 @@ static int __sev_snp_shutdown_locked(int *error, bool panic) 
	sev->snp_initialized = false;

	dev_dbg(sev->dev, "SEV-SNP firmware shutdown\n");



	/*

	 * __sev_snp_shutdown_locked() deadlocks when it tries to unregister

	 * itself during panic as the panic notifier is called with RCU read

	 * lock held and notifier unregistration does RCU synchronization.

	 */

	if (!panic)

		atomic_notifier_chain_unregister(&panic_notifier_list,

						 &snp_panic_notifier);