linux-kernel - Re: [PATCH] ARM: crypto: work around gcc-15 warning

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Message-ID: <aFkbpCBUr-ujNMCF@gondor.apana.org.au>
Date: Mon, 23 Jun 2025 17:17:24 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Arnd Bergmann <arnd@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Russell King <linux@...linux.org.uk>,
	Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Eric Biggers <ebiggers@...gle.com>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: crypto: work around gcc-15 warning

On Tue, Jun 10, 2025 at 11:32:52AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> I get a very rare -Wstringop-overread warning with gcc-15 for one function
> in aesbs_ctr_encrypt():
> 
> arch/arm/crypto/aes-neonbs-glue.c: In function 'ctr_encrypt':
> arch/arm/crypto/aes-neonbs-glue.c:212:1446: error: '__builtin_memcpy' offset [17, 2147483647] is out of the bounds [0, 16] of object 'buf' with type 'u8[16]' {aka 'unsigned char[16]'} [-Werror=array-bounds=]
>   212 |                         src = dst = memcpy(buf + sizeof(buf) - bytes,
> arch/arm/crypto/aes-neonbs-glue.c: In function 'ctr_encrypt':
> arch/arm/crypto/aes-neonbs-glue.c:218:17: error: 'aesbs_ctr_encrypt' reading 1 byte from a region of size 0 [-Werror=stringop-overread]
>   218 |                 aesbs_ctr_encrypt(dst, src, ctx->rk, ctx->rounds, bytes, walk.iv);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/arm/crypto/aes-neonbs-glue.c:218:17: note: referencing argument 2 of type 'const u8[0]' {aka 'const unsigned char[]'}
> arch/arm/crypto/aes-neonbs-glue.c:218:17: note: referencing argument 3 of type 'const u8[0]' {aka 'const unsigned char[]'}
> arch/arm/crypto/aes-neonbs-glue.c:218:17: note: referencing argument 6 of type 'u8[0]' {aka 'unsigned char[]'}
> arch/arm/crypto/aes-neonbs-glue.c:36:17: note: in a call to function 'aesbs_ctr_encrypt'
>    36 | asmlinkage void aesbs_ctr_encrypt(u8 out[], u8 const in[], u8 const rk[],
> 
> This could happen in theory if walk.nbytes is larger than INT_MAX and gets
> converted to a negative local variable.
> 
> Keep the type unsigned like the orignal nbytes to be sure there is no
> integer overflow.
> 
> Fixes: c8bf850e991a ("crypto: arm/aes-neonbs-ctr - deal with non-multiples of AES block size")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm/crypto/aes-neonbs-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