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

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Date: Tue, 21 Nov 2023 12:52:44 -0600
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>
Cc: linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org
Subject: [PATCH][next] powerpc/crypto: Avoid -Wstringop-overflow warnings

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(-)

diff --git a/arch/powerpc/crypto/aes-gcm-p10-glue.c b/arch/powerpc/crypto/aes-gcm-p10-glue.c
index 4b6e899895e7..f62ee54076c0 100644
--- a/arch/powerpc/crypto/aes-gcm-p10-glue.c
+++ b/arch/powerpc/crypto/aes-gcm-p10-glue.c
@@ -37,7 +37,7 @@ asmlinkage void aes_p10_gcm_encrypt(u8 *in, u8 *out, size_t len,
 				    void *rkey, u8 *iv, void *Xi);
 asmlinkage void aes_p10_gcm_decrypt(u8 *in, u8 *out, size_t len,
 				    void *rkey, u8 *iv, void *Xi);
-asmlinkage void gcm_init_htable(unsigned char htable[256], unsigned char Xi[16]);
+asmlinkage void gcm_init_htable(unsigned char htable[], unsigned char Xi[]);
 asmlinkage void gcm_ghash_p10(unsigned char *Xi, unsigned char *Htable,
 		unsigned char *aad, unsigned int alen);
 
-- 
2.34.1