[PATCH] crypto: ccp: Fix SNP panic notifier unregistration

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

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.

Fix SNP panic notifier to unregister itself during module unload
if SNP is initialized.

Fixes: 19860c3274fb ("crypto: ccp - Register SNP panic notifier only if SNP is enabled")
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 drivers/crypto/ccp/sev-dev.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 8fb94c5f006a..942d93da1136 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1787,9 +1787,6 @@ static int __sev_snp_shutdown_locked(int *error, bool panic)
 	sev->snp_initialized = false;
 	dev_dbg(sev->dev, "SEV-SNP firmware shutdown\n");
 
-	atomic_notifier_chain_unregister(&panic_notifier_list,
-					 &snp_panic_notifier);
-
 	/* Reset TMR size back to default */
 	sev_es_tmr_size = SEV_TMR_SIZE;
 
@@ -2562,4 +2559,8 @@ void sev_pci_exit(void)
 		return;
 
 	sev_firmware_shutdown(sev);
+
+	if (sev->snp_initialized)
+		atomic_notifier_chain_unregister(&panic_notifier_list,
+						 &snp_panic_notifier);
 }
-- 
2.34.1