From: Al Viro <viro@ZenIV.linux.org.uk>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Michal Hocko <mhocko@suse.cz>, Sergey Dyasly <dserrg@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/4] proc: avoid ->f_pos overflows in proc_task_readdir() paths
Date: Tue, 4 Jun 2013 01:58:53 +0100 [thread overview]
Message-ID: <20130604005853.GA13110@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20130603190705.GA11517@redhat.com>
On Mon, Jun 03, 2013 at 09:07:05PM +0200, Oleg Nesterov wrote:
> 1. proc_task_readdir() truncates f_pos to long, this can lead
> to wrong result on 32bit.
>
> 2. first_tid() truncates f_pos to int, this is wrong even on
> 64bit.
>
> We could check that f_pos < PID_MAX or even INT_MAX in
> proc_task_readdir(), but this patch simply checks the
> potential overflow in first_tid(), this check is nop on
> 64bit. We do not care if it was negative and the new
> unsigned value is huge, all we need to ensure is that we
> never wrongly return !NULL.
>
> 3. Remove the 2nd "nr != 0" check before get_nr_threads(),
> nr_threads == 0 is not distinguishable from !pid_task()
> above.
Oleg, please take a look at the series in vfs.git#experimental; at the very
least, we don't want to access file->f_pos in any foo_readdir() - it's too
messy and race-prone. It's pretty much independent from the issues you
are dealing with, but let's avoid creating pointless conflicts...
next prev parent reply other threads:[~2013-06-04 0:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-03 19:06 [PATCH v2 0/4] proc: first_tid() fix/cleanup Oleg Nesterov
2013-06-03 19:06 ` [PATCH v2 1/4] proc: first_tid: fix the potential use-after-free Oleg Nesterov
2013-06-03 19:07 ` [PATCH v2 2/4] proc: change first_tid() to use while_each_thread() Oleg Nesterov
2013-06-03 19:07 ` [PATCH v2 3/4] proc: simplify proc_task_readdir/first_tid paths Oleg Nesterov
2013-06-03 22:06 ` Eric W. Biederman
2013-06-03 19:07 ` [PATCH v2 4/4] proc: avoid ->f_pos overflows in proc_task_readdir() paths Oleg Nesterov
2013-06-03 22:18 ` Eric W. Biederman
2013-06-04 17:14 ` Oleg Nesterov
2013-06-04 17:39 ` Al Viro
2013-06-04 19:57 ` Oleg Nesterov
2013-06-04 21:06 ` Al Viro
2013-06-04 0:58 ` Al Viro [this message]
2013-06-04 17:35 ` Oleg Nesterov
2013-06-04 17:32 ` [PATCH v2 0/4] proc: first_tid() fix/cleanup Oleg Nesterov
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