From: Kees Cook <keescook@chromium.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>,
Justin Stitt <justinstitt@google.com>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <nathan@kernel.org>,
Bill Wendling <morbo@google.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3] fs: fix unintentional arithmetic wraparound in offset calculation
Date: Fri, 17 May 2024 14:24:17 -0700 [thread overview]
Message-ID: <202405171417.B290C50A@keescook> (raw)
In-Reply-To: <20240517012647.GN2118490@ZenIV>
On Fri, May 17, 2024 at 02:26:47AM +0100, Al Viro wrote:
> On Fri, May 17, 2024 at 02:13:22AM +0100, Matthew Wilcox wrote:
> > On Fri, May 17, 2024 at 12:29:06AM +0000, Justin Stitt wrote:
> > > When running syzkaller with the newly reintroduced signed integer
> > > overflow sanitizer we encounter this report:
> >
> > why do you keep saying it's unintentional? it's clearly intended.
>
> Because they are short on actual bugs to be found by their tooling
> and attempt to inflate the sound/noise rate; therefore, every time
"short on bugs"? We're trying to drive it to zero. I would *love* to be
short on bugs. See my reply[1] to Ted.
> when overflow _IS_ handled correctly, it must have been an accident -
> we couldn't have possibly done the analysis correctly. And if somebody
> insists that they _are_ capable of basic math, they must be dishonest.
> So... "unintentional" it's going to be.
As Justin said, this is a poor choice in wording. In other cases I've
tried to describe this as making changes so that intent is unambiguous
(to both a human and a compiler).
> <southpark> Math is hard, mmkay? </southpark>
>
> Al, more than slightly annoyed by that aspect of the entire thing...
I'm sorry about that. None of this is a commentary on code correctness;
we're just trying to refactor things so that the compiler can help us
catch the _unintended_ overflows. This one is _intended_, so here we are
to find a palatable way to leave the behavior unchanged while gaining
compiler coverage.
-Kees
[1] https://lore.kernel.org/linux-hardening/202405171329.019F2F566C@keescook/
--
Kees Cook
next prev parent reply other threads:[~2024-05-17 21:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-17 0:29 [PATCH v3] fs: fix unintentional arithmetic wraparound in offset calculation Justin Stitt
2024-05-17 1:13 ` Matthew Wilcox
2024-05-17 1:26 ` Al Viro
2024-05-17 1:32 ` Matthew Wilcox
2024-05-17 21:24 ` Kees Cook [this message]
2024-05-17 20:40 ` Justin Stitt
2024-05-20 11:58 ` Jan Kara
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