linux-kernel - Re: [RESEND PATCH v3] crypto: ccp: Fix SNP panic notifier unregistration

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Message-ID: <aFkdYX1tZsESRpne@gondor.apana.org.au>
Date: Mon, 23 Jun 2025 17:24:49 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Ashish Kalra <Ashish.Kalra@....com>
Cc: thomas.lendacky@....com, john.allen@....com, davem@...emloft.net,
	aik@....com, dionnaglaze@...gle.com, michael.roth@....com,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [RESEND PATCH v3] crypto: ccp: Fix SNP panic notifier
 unregistration

On Mon, Jun 16, 2025 at 09:50:27PM +0000, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> 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@....com>
> Cc: stable@...r.kernel.org
> Fixes: 19860c3274fb ("crypto: ccp - Register SNP panic notifier only if SNP is enabled")
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt