linux-kernel - Re: [PATCH] crypto: Prevent kernel-infoleak in rng

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aKBMjQpA9P70EA0z@gondor.apana.org.au>
Date: Sat, 16 Aug 2025 17:17:01 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Edward Adam Davis <eadavis@...com>
Cc: syzbot+e8bcd7ee3db6cb5cb875@...kaller.appspotmail.com,
	davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] crypto: Prevent kernel-infoleak in rng_recvmsg

On Sat, Aug 09, 2025 at 05:59:43PM +0800, Edward Adam Davis wrote:
> Initialize the intermediary array member to 0 to prevent the kernel from
> leaking uninitialized data to user space.
> 
> Reported-by: syzbot+e8bcd7ee3db6cb5cb875@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=e8bcd7ee3db6cb5cb875
> Tested-by: syzbot+e8bcd7ee3db6cb5cb875@...kaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
>  crypto/jitterentropy-kcapi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
> index c24d4ff2b4a8..9e9e069f55af 100644
> --- a/crypto/jitterentropy-kcapi.c
> +++ b/crypto/jitterentropy-kcapi.c
> @@ -107,7 +107,7 @@ int jent_hash_time(void *hash_state, __u64 time, u8 *addtl,
>  {
>  	struct shash_desc *hash_state_desc = (struct shash_desc *)hash_state;
>  	SHASH_DESC_ON_STACK(desc, hash_state_desc->tfm);
> -	u8 intermediary[SHA3_256_DIGEST_SIZE];
> +	u8 intermediary[SHA3_256_DIGEST_SIZE] = { 0 };

This is not a leak! The stack memroy is hashed and fed into the
entropy pool.  If you can recover the original kernel memory from
the result, then we have much bigger problems :)

Please find a way to mark this as a false positive.

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