linux-kernel - Re: [PATCH V2] crypto: Mark intermediary memory as clean

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Message-ID: <aKG_yEuG6F4cqFjf@gondor.apana.org.au>
Date: Sun, 17 Aug 2025 19:40:56 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Edward Adam Davis <eadavis@...com>
Cc: davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+e8bcd7ee3db6cb5cb875@...kaller.appspotmail.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V2] crypto: Mark intermediary memory as clean

On Sun, Aug 17, 2025 at 06:59:15PM +0800, Edward Adam Davis wrote:
> This is not a leak! The stack memroy is hashed and fed into the
> entropy pool. We can't recover the original kernel memory from it.
> 
> Reported-by: syzbot+e8bcd7ee3db6cb5cb875@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=e8bcd7ee3db6cb5cb875
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
> V1 -> V2: mark it as unpoison
> 
>  crypto/jitterentropy-kcapi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
> index 1266eb790708..4020a6e41b0e 100644
> --- a/crypto/jitterentropy-kcapi.c
> +++ b/crypto/jitterentropy-kcapi.c
> @@ -117,6 +117,7 @@ int jent_hash_time(void *hash_state, __u64 time, u8 *addtl,
>  		pr_warn_ratelimited("Unexpected digest size\n");
>  		return -EINVAL;
>  	}
> +	kmsan_unpoison_memory(intermediary, SHA3_256_DIGEST_SIZE);

Please change SHA3_256_DIGEST_SIZE to sizeof(intermediary).

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