Re: [PATCH v1 1/1] s390/crypto: Generate intermediate CV for API partial block handling

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Hardware Alignment Requirement Violation due to `__packed` attribute
--

--- Patch [1]: [PATCH v1 1/1] s390/crypto: Generate intermediate CV for API partial block handling ---
commit 6ca29d2947b71c2e1420feb8fbee6504922ff37f
Author: Holger Dengler <dengler@linux.ibm.com>

s390/crypto: Generate intermediate CV for API partial block handling

This commit updates the internal hash_data() function to conditionally use
cpacf_kimd() for intermediate chaining values when API partial block handling
is requested, reserving cpacf_klmd() for the final hash value.

> diff --git a/arch/s390/crypto/hmac_s390.c b/arch/s390/crypto/hmac_s390.c
> index f8cd09f341d4b..445fa7bbd9586 100644
> --- a/arch/s390/crypto/hmac_s390.c
> +++ b/arch/s390/crypto/hmac_s390.c
> @@ -150,7 +150,10 @@ static int hash_data(const u8 *in, unsigned int inlen,
>  
>  #undef PARAM_INIT
>  
> -	cpacf_klmd(func, &param, in, inlen);
> +	if (final)
> +		cpacf_klmd(func, &param, in, inlen);
> +	else
> +		cpacf_kimd(func, &param, in, inlen);

[Severity: High]
This is a pre-existing issue, but could the alignment of the param block passed
to cpacf_kimd() and cpacf_klmd() trigger a hardware specification exception?

The param variable is defined earlier in hash_data() with the __packed
attribute:

	union {
		struct sha256_paramblock {
			u32 h[8];
			u64 mbl;
		} sha256;
		struct sha512_paramblock {
			u64 h[8];
			u128 mbl;
		} sha512;
	} __packed param;

The __packed attribute reduces the compiler's alignment requirement for param
to 1 byte. The z/Architecture requires doubleword (8-byte) alignment for KIMD
and KLMD parameter blocks.

If the compiler places param on a stack address not divisible by 8, won't this
cause a kernel panic when passed to these hardware instructions? 

Since the struct fields inside the union are naturally packed, can we remove
the __packed attribute to ensure the compiler maintains safe alignment?

>  
>  	memcpy(digest, &param, digestsize);
>

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260814142010.259918-2-dengler@linux.ibm.com?part=1