From: Bodo Eggert <7eggert@gmx.de>
To: "Michael K. Edwards" <medwards.linux@gmail.com>,
Eric Dumazet <dada1@cosmosbay.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: sys_write() racy for multi-threaded append?
Date: Mon, 12 Mar 2007 08:53:31 +0100 [thread overview]
Message-ID: <E1HQfLX-0000fk-68@be1.lrz> (raw)
In-Reply-To: 7WBt7-3SZ-23@gated-at.bofh.it
Michael K. Edwards <medwards.linux@gmail.com> wrote:
> On 3/8/07, Eric Dumazet <dada1@cosmosbay.com> wrote:
>> Absolutely not. We dont want to slow down kernel 'just in case a fool might
>> want to do crazy things'
>
> Actually, I think it would make the kernel (negligibly) faster to bump
> f_pos before the vfs_write() call.
This is a security risk.
----------------
other process:
unlink(secrest_file)
Thread 1:
write(fd, large)
(interrupted)
Thread 2:
fseek(fd, -n, relative)
read(fd, buf)
----------------
BTW: The best thing you can do to a program where two threads race for
writing one fd is to let it crash and burn in the most spectacular way
allowed without affecting the rest of the system, unless it happens to
be a pipe and the number of bytes written is less than PIPE_MAX.
--
The secret of the universe is #@*%! NO CARRIER
Friß, Spammer: dyIw3Rs@x.7eggert.dyndns.org PLxmr@lv.7eggert.dyndns.org
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next parent reply other threads:[~2007-03-12 7:54 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <7WzUo-1zl-21@gated-at.bofh.it>
[not found] ` <7WAx2-2pg-21@gated-at.bofh.it>
[not found] ` <7WAGF-2Bx-9@gated-at.bofh.it>
[not found] ` <7WB07-3g5-33@gated-at.bofh.it>
[not found] ` <7WBt7-3SZ-23@gated-at.bofh.it>
2007-03-12 7:53 ` Bodo Eggert [this message]
2007-03-12 16:26 ` sys_write() racy for multi-threaded append? Michael K. Edwards
2007-03-12 18:48 ` Bodo Eggert
2007-03-13 0:46 ` Michael K. Edwards
2007-03-13 2:24 ` Alan Cox
2007-03-13 7:25 ` Michael K. Edwards
2007-03-13 7:42 ` David Miller
2007-03-13 16:24 ` Michael K. Edwards
2007-03-13 17:59 ` Michael K. Edwards
2007-03-13 19:09 ` Christoph Hellwig
2007-03-13 23:40 ` Michael K. Edwards
2007-03-14 0:09 ` Michael K. Edwards
2007-03-13 13:15 ` Alan Cox
2007-03-14 20:09 ` Michael K. Edwards
2007-03-16 16:43 ` Frank Ch. Eigler
2007-03-16 17:25 ` Alan Cox
2007-03-13 14:00 ` David M. Lloyd
2007-03-08 23:08 Michael K. Edwards
2007-03-08 23:43 ` Eric Dumazet
2007-03-08 23:57 ` Michael K. Edwards
2007-03-09 0:15 ` Eric Dumazet
2007-03-09 0:45 ` Michael K. Edwards
2007-03-09 1:34 ` Benjamin LaHaise
2007-03-09 12:19 ` Michael K. Edwards
2007-03-09 13:44 ` Eric Dumazet
2007-03-09 14:10 ` Alan Cox
2007-03-09 14:59 ` Benjamin LaHaise
2007-03-10 6:43 ` Michael K. Edwards
2007-03-09 5:53 ` Eric Dumazet
2007-03-09 11:52 ` Michael K. Edwards
2007-03-09 0:43 ` Alan Cox
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