From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
linux-kernel@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>
Subject: Re: [PATCH v1 2/6] lib: scanf: handle integer overflows in vsscanf
Date: Sun, 10 Mar 2019 22:06:27 +0100 [thread overview]
Message-ID: <9da44b6b-49c1-3383-e272-d61065f81de4@rasmusvillemoes.dk> (raw)
In-Reply-To: <155223699287.4075.13184771244455866778.stgit@buzz>
On 10/03/2019 17.56, Konstantin Khlebnikov wrote:
> Traditional scanf implementations ignore integer overflows because
> C language standard allows here undefined behavior (§7.21.6.2 #10).
>
> So, sane and safe behavior wouldn't harm anything.
>
> This patch carefully checks integer overflows and stops matching if result
> does not fit into appropriate type before assigning it into argument.
IIRC, this has been attempted before, causing a userspace regression
because some sysfs/procfs file matched with %u or %x, and somebody wrote
-1 to get 0xffffffff .
I can't remember or find a reference right now, making the above a
rather weak argument. However, please start the series with your test
cases, before any refactoring. That makes it easier to see what
behaviour you're changing (i.e., what used to be allowed is now treated
as non-match, etc.).
Rasmus
next prev parent reply other threads:[~2019-03-10 21:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-10 16:56 [PATCH v1 0/6] Make sscanf safer Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 1/6] lib: scanf: document features of scanf format string Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 2/6] lib: scanf: handle integer overflows in vsscanf Konstantin Khlebnikov
2019-03-10 21:06 ` Rasmus Villemoes [this message]
2019-03-10 21:52 ` Linus Torvalds
2019-03-11 7:22 ` Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 3/6] lib: scanf: add vsscanf feature for matching end of text Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 4/6] lib: scanf: handle character ranges in %[...] Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 5/6] lib: scanf: mark sscanf and vsscanf as __must_check Konstantin Khlebnikov
2019-03-10 16:56 ` [PATCH v1 6/6] lib: scanf: add test module Konstantin Khlebnikov
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