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 for Android: free password hash cracker in your pocket

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

Message-ID: <alpine.LFD.1.10.0806170947380.25099@woody.linux-foundation.org>
Date:	Tue, 17 Jun 2008 10:08:24 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Bron Gondwana <brong@...tmail.fm>
cc:	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>
Subject: Re: BUG: mmapfile/writev spurious zero bytes (x86_64/not i386,
 bisected, reproducable)



On Tue, 17 Jun 2008, Bron Gondwana wrote:
> 
> And I appear to have sent the one without the usage comments at the top.
> Here they are:

Very interesting. There's certainly something there. 

That said, there's a distracting bug which is visible when doing an strace

 lseek(4, 140333890921392, SEEK_SET)     = -1 EINVAL (Invalid argument)
 write(4, "\0\0\0\0", 4)                 = 4

which is from that

	lseek(newfd, mapbase + offset + size - 8, 0);
	write(newfd, (char *) &zero, 4);

where the addition of "mapbase" is insane. So that will write zeroes to 
the wrong part of the file (offset 64, to be exact). And that will get 
overwritten by the next write, making it all look entirely insane.

That said, that bug may be distracting, but it seems to have nothign at 
all to do with the actual problem. The bug seems to happen only when the 
file is not pre-paged in.

Nick?

		Linus
--
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/