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crypto: ccp - Fix SNP panic notifier unregistration

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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: Tom Lendacky <thomas.lendacky@amd.com>
Cc: stable@vger.kernel.org
Fixes: 19860c3274 ("crypto: ccp - Register SNP panic notifier only if SNP is enabled")
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ashish Kalra
2025-06-16 21:50:27 +00:00
committed by Herbert Xu
parent f5ad93ffb5
commit ab8b9fd39c
1 changed files with 8 additions and 2 deletions
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10
drivers/crypto/ccp/sev-dev.c
View File

@@ -1787,8 +1787,14 @@ 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);
/*
* __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);
/* Reset TMR size back to default */
sev_es_tmr_size = SEV_TMR_SIZE;