linux-kernel - Re: BUG: mmapfile/writev spurious zero bytes (x86

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: <20080618022712.GB1383@brong.net>
Date:	Wed, 18 Jun 2008 12:27:12 +1000
From:	Bron Gondwana <brong@...tmail.fm>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Bron Gondwana <brong@...tmail.fm>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rob Mueller <robm@...tmail.fm>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: BUG: mmapfile/writev spurious zero bytes (x86_64/not i386,
	bisected, reproducable)

On Tue, Jun 17, 2008 at 02:20:49PM -0700, Linus Torvalds wrote:
> 
> 
> On Tue, 17 Jun 2008, Linus Torvalds wrote:
> > 
> > Hmm. Something like this *may* salvage it.
> > 
> > Untested, so far (I'll reboot and test soon enough), but even if it fixes 
> > things, it's not really very good. 
> 
> Ok, so I just rebooted with this, and it does indeed fix the bug.
> 
> I'd be happier with a more complete fix (ie being byte-accurate and 
> actually doing the partial copy when it hits a fault in the middle), but 
> this seems to be the minimal fix, and at least fixes the totally bogus 
> return values from the x86-64 __copy_user*() functions.
> 
> Not that I checked that I got _all_ cases correct (and maybe there are 
> other versions of __copy_user that I missed entirely), but Bron's 
> test-case at least seems to work properly for me now.
> 
> Bron? If you have a more complete test-suite (ie the real-world case that 
> made you find this), it would be good to verify the whole thing. 

I have a real world test case using "cyr_dbtool" from Cyrus 2.3.12 on a
known-bug-inducing piece of data (the key and value sizes in the example
code were taken from that.  Indeed, the example code started off
building byte-for-byte identical files, then I changed it to write only
a single character across the entire key and value so the hexdump was
shorter)

I'll give it a go.

Bron.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/