linux-kernel - Re: [PATCH][next] powerpc/crypto: Avoid -Wstringop-overflow warnings

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Message-ID: <ZWmxpmuBcAhsE1wf@gondor.apana.org.au>
Date:   Fri, 1 Dec 2023 18:12:54 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] powerpc/crypto: Avoid -Wstringop-overflow warnings

On Tue, Nov 21, 2023 at 12:52:44PM -0600, Gustavo A. R. Silva wrote:
> The compiler doesn't know that `32` is an offset into the Hash table:
> 
>  56 struct Hash_ctx {
>  57         u8 H[16];       /* subkey */
>  58         u8 Htable[256]; /* Xi, Hash table(offset 32) */
>  59 };
> 
> So, it legitimately complains about a potential out-of-bounds issue
> if `256 bytes` are accessed in `htable` (this implies going
> `32 bytes` beyond the boundaries of `Htable`):
> 
> arch/powerpc/crypto/aes-gcm-p10-glue.c: In function 'gcmp10_init':
> arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: error: 'gcm_init_htable' accessing 256 bytes in a region of size 224 [-Werror=stringop-overflow=]
>   120 |         gcm_init_htable(hash->Htable+32, hash->H);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: note: referencing argument 1 of type 'unsigned char[256]'
> arch/powerpc/crypto/aes-gcm-p10-glue.c:120:9: note: referencing argument 2 of type 'unsigned char[16]'
> arch/powerpc/crypto/aes-gcm-p10-glue.c:40:17: note: in a call to function 'gcm_init_htable'
>    40 | asmlinkage void gcm_init_htable(unsigned char htable[256], unsigned char Xi[16]);
>       |                 ^~~~~~~~~~~~~~~
> 
> Address this by avoiding specifying the size of `htable` in the function
> prototype; and just for consistency, do the same for parameter `Xi`.
> 
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Closes: https://lore.kernel.org/linux-next/20231121131903.68a37932@canb.auug.org.au/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  arch/powerpc/crypto/aes-gcm-p10-glue.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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