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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHmME9pvgyot-PJDbWu1saYagEYutddc_B9qNHf-MZ-vkw4zoQ@mail.gmail.com>
Date: Wed, 19 Nov 2025 17:46:44 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: kernel test robot <lkp@...el.com>, Eric Biggers <ebiggers@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, 
	Kees Cook <kees@...nel.org>, linux-crypto@...r.kernel.org, llvm@...ts.linux.dev, 
	oe-kbuild-all@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH libcrypto 2/2] crypto: chacha20poly1305: statically check
 fixed array lengths

Hey Linus,

On Wed, Nov 19, 2025 at 5:29 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
>  On Wed, 19 Nov 2025 at 04:46, kernel test robot <lkp@...el.com> wrote:
> >
> > >> drivers/net/wireguard/cookie.c:193:2: warning: array argument is too small; contains 31 elements, callee requires at least 32 [-Warray-bounds]
>
> Hmm. Is this a compiler bug?

It's not. It's a 0day test bot bug! My original patch had in it some
commentary about what a bug would look like when it's caught by the
compiler. In order to provoke that compiler output, I mentioned in the
commit message that this diff will produce such and such result:

diff --git a/drivers/net/wireguard/cookie.h b/drivers/net/wireguard/cookie.h
index c4bd61ca03f2..2839c46029f8 100644
--- a/drivers/net/wireguard/cookie.h
+++ b/drivers/net/wireguard/cookie.h
@@ -13,7 +13,7 @@ struct wg_peer;

 struct cookie_checker {
        u8 secret[NOISE_HASH_LEN];
-       u8 cookie_encryption_key[NOISE_SYMMETRIC_KEY_LEN];
+       u8 cookie_encryption_key[NOISE_SYMMETRIC_KEY_LEN - 1];
        u8 message_mac1_key[NOISE_SYMMETRIC_KEY_LEN];
        u64 secret_birthdate;
        struct rw_semaphore secret_lock;

It looks like the 0day test bot just went through the email and
applied all the `diff --git ...` hunks, without taking into account
the context area above where the actual patches start.

So, if anything, this test bot output is showing that the compiler
feature works as intended.

Jason