From: Junio C Hamano <gitster@pobox•com>
To: "Carlos Martín Nieto" <cmn@elego•de>
Cc: git@vger•kernel.org, Jeff King <peff@peff•net>
Subject: Re: [PATCH] valgrind: ignore SSE-based strlen invalid reads
Date: Wed, 16 Mar 2011 13:18:04 -0700 [thread overview]
Message-ID: <7vr5a67rb7.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <1300275961-5798-1-git-send-email-cmn@elego.de> ("Carlos Martín Nieto"'s message of "Wed, 16 Mar 2011 12:46:01 +0100")
Carlos Martín Nieto <cmn@elego•de> writes:
> Some versions of strlen use SSE to speed up the calculation and load 4
> bytes at a time, even if it means reading past the end of the
> allocated memory. This read is safe and when the strlen function is
> inlined, it is not replaced by valgrind, which reports a
> false-possitive.
>
> Tell valgrind to ignore this particular error, as the read is, in
> fact, safe. Current upstream-released version 2.6.1 is affected. Some
> distributions have this fixed in their latest versions.
>
> Signed-off-by: Carlos Martín Nieto <cmn@elego•de>
> ---
>
>>> I think 3.6.1 doesn't need it, as Debian's 1:3.5.0+3.6.0svn20100609-1
>>> version is reportedly fixed.
>>
>>Ah, nice. A phrase like "some versions of valgrind before 3.6.1"
>>would be fine with me fwiw. :)
>
> I just downloaded and compiled the upstream release 2.6.1 and it's
> still affected (it does fix some other related
> false-positives). Fedorea rawhide has the fix in, according to their
> bug tracker. I haven't tested the reportedly-fixed version in Debian
> yet.
I take it that you meant 3.6.1 in both places above?
This somehow reminds me of my past life where I saw a buggy implementation
of strlen() in the C library loaded one word too many from memory, and
segfaulted even when the string ended before the end of a mapped page when
the next page was unmapped.
Anyway, nice digging.
next prev parent reply other threads:[~2011-03-16 20:18 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-16 9:31 [PATCH] valgrind: ignore SSE-based strlen invalid reads Carlos Martín Nieto
2011-03-16 9:56 ` Jonathan Nieder
2011-03-16 10:41 ` Carlos Martín Nieto
2011-03-16 10:47 ` Carlos Martín Nieto
2011-03-16 10:52 ` Jonathan Nieder
2011-03-16 11:10 ` Carlos Martín Nieto
2011-03-16 11:25 ` Jonathan Nieder
2011-03-16 11:46 ` Carlos Martín Nieto
2011-03-16 20:18 ` Junio C Hamano [this message]
2011-03-16 20:44 ` Carlos Martín Nieto
2011-03-16 22:43 ` Andreas Schwab
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7vr5a67rb7.fsf@alter.siamese.dyndns.org \
--to=gitster@pobox$(echo .)com \
--cc=cmn@elego$(echo .)de \
--cc=git@vger$(echo .)kernel.org \
--cc=peff@peff$(echo .)net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox