Re: [PATCH libcrypto 2/2] crypto: chacha20poly1305: statically check fixed array lengths

[kernel test robot <lkp@intel.com>]

Hi Jason,

kernel test robot noticed the following build warnings:

[auto build test WARNING on herbert-cryptodev-2.6/master]
[also build test WARNING on herbert-crypto-2.6/master ebiggers/libcrypto-next ebiggers/libcrypto-fixes linus/master linux/master v6.18-rc6 next-20251119]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Jason-A-Donenfeld/crypto-chacha20poly1305-statically-check-fixed-array-lengths/20251119-011125
base:   https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git master
patch link:    https://lore.kernel.org/r/20251118170240.689299-2-Jason%40zx2c4.com
patch subject: [PATCH libcrypto 2/2] crypto: chacha20poly1305: statically check fixed array lengths
config: m68k-defconfig (https://download.01.org/0day-ci/archive/20251119/202511191846.AAKP7VQw-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251119/202511191846.AAKP7VQw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511191846.AAKP7VQw-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/net/wireguard/cookie.c: In function 'wg_cookie_message_create':
>> drivers/net/wireguard/cookie.c:193:9: warning: 'xchacha20poly1305_encrypt' reading 32 bytes from a region of size 31 [-Wstringop-overread]
     193 |         xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN,
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     194 |                                   macs->mac1, COOKIE_LEN, dst->nonce,
         |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     195 |                                   checker->cookie_encryption_key);
         |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/wireguard/cookie.c:193:9: note: referencing argument 7 of type 'const u8[32]' {aka 'const unsigned char[32]'}
   In file included from drivers/net/wireguard/messages.h:10,
                    from drivers/net/wireguard/cookie.h:9,
                    from drivers/net/wireguard/cookie.c:6:
   include/crypto/chacha20poly1305.h:29:6: note: in a call to function 'xchacha20poly1305_encrypt'
      29 | void xchacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/xchacha20poly1305_encrypt +193 drivers/net/wireguard/cookie.c

e7096c131e5161f Jason A. Donenfeld 2019-12-09  179  
e7096c131e5161f Jason A. Donenfeld 2019-12-09  180  void wg_cookie_message_create(struct message_handshake_cookie *dst,
e7096c131e5161f Jason A. Donenfeld 2019-12-09  181  			      struct sk_buff *skb, __le32 index,
e7096c131e5161f Jason A. Donenfeld 2019-12-09  182  			      struct cookie_checker *checker)
e7096c131e5161f Jason A. Donenfeld 2019-12-09  183  {
e7096c131e5161f Jason A. Donenfeld 2019-12-09  184  	struct message_macs *macs = (struct message_macs *)
e7096c131e5161f Jason A. Donenfeld 2019-12-09  185  		((u8 *)skb->data + skb->len - sizeof(*macs));
e7096c131e5161f Jason A. Donenfeld 2019-12-09  186  	u8 cookie[COOKIE_LEN];
e7096c131e5161f Jason A. Donenfeld 2019-12-09  187  
e7096c131e5161f Jason A. Donenfeld 2019-12-09  188  	dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE);
e7096c131e5161f Jason A. Donenfeld 2019-12-09  189  	dst->receiver_index = index;
e7096c131e5161f Jason A. Donenfeld 2019-12-09  190  	get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
e7096c131e5161f Jason A. Donenfeld 2019-12-09  191  
e7096c131e5161f Jason A. Donenfeld 2019-12-09  192  	make_cookie(cookie, skb, checker);
e7096c131e5161f Jason A. Donenfeld 2019-12-09 @193  	xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN,
e7096c131e5161f Jason A. Donenfeld 2019-12-09  194  				  macs->mac1, COOKIE_LEN, dst->nonce,
e7096c131e5161f Jason A. Donenfeld 2019-12-09  195  				  checker->cookie_encryption_key);
e7096c131e5161f Jason A. Donenfeld 2019-12-09  196  }
e7096c131e5161f Jason A. Donenfeld 2019-12-09  197  

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