linux-kernel - Re: [PATCH] crypto: s390/sha - Fix uninitialized variable in SHA-1 and SHA-2

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Message-ID: <20250703172032.GA2284@sol>
Date: Thu, 3 Jul 2025 10:20:32 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
	Harald Freudenberger <freude@...ux.ibm.com>,
	Holger Dengler <dengler@...ux.ibm.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Joerg Schmidbauer <jschmidb@...ibm.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>, stable@...r.kernel.org,
	Ingo Franzki <ifranzki@...ux.ibm.com>
Subject: Re: [PATCH] crypto: s390/sha - Fix uninitialized variable in SHA-1
 and SHA-2

On Fri, Jun 27, 2025 at 11:56:49AM -0700, Eric Biggers wrote:
> Commit 88c02b3f79a6 ("s390/sha3: Support sha3 performance enhancements")
> added the field s390_sha_ctx::first_message_part and made it be used by
> s390_sha_update_blocks().  At the time, s390_sha_update_blocks() was
> used by all the s390 SHA-1, SHA-2, and SHA-3 algorithms.  However, only
> the initialization functions for SHA-3 were updated, leaving SHA-1 and
> SHA-2 using first_message_part uninitialized.
> 
> This could cause e.g. CPACF_KIMD_SHA_512 | CPACF_KIMD_NIP to be used
> instead of just CPACF_KIMD_NIP.  It's unclear why this didn't cause a
> problem earlier; this bug was found only when UBSAN detected the
> uninitialized boolean.  Perhaps the CPU ignores CPACF_KIMD_NIP for SHA-1
> and SHA-2.  Regardless, let's fix this.  For now just initialize to
> false, i.e. don't try to "optimize" the SHA state initialization.
> 
> Note: in 6.16, we need to patch SHA-1, SHA-384, and SHA-512.  In 6.15
> and earlier, we'll also need to patch SHA-224 and SHA-256, as they
> hadn't yet been librarified (which incidentally fixed this bug).
> 
> Fixes: 88c02b3f79a6 ("s390/sha3: Support sha3 performance enhancements")
> Cc: stable@...r.kernel.org
> Reported-by: Ingo Franzki <ifranzki@...ux.ibm.com>
> Closes: https://lore.kernel.org/r/12740696-595c-4604-873e-aefe8b405fbf@linux.ibm.com
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
> ---
> 
> This is targeting 6.16.  I'd prefer to take this through
> libcrypto-fixes, since the librarification work is also touching this
> area.  But let me know if there's a preference for the crypto tree or
> the s390 tree instead.
> 
>  arch/s390/crypto/sha1_s390.c   | 1 +
>  arch/s390/crypto/sha512_s390.c | 2 ++
>  2 files changed, 3 insertions(+)

I just realized this patch is incomplete: it updated s390_sha1_init(),
sha384_init(), and sha512_init(), but not s390_sha1_import() and sha512_import()
which need the same fix...  I'll send a v2.

- Eric