linux-kernel - Re: [PATCH] vfs: check i_count under lock in evict

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]

Date:	Tue, 12 Jul 2016 01:46:23 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Chunwei Chen <david.chen@...exus.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] vfs: check i_count under lock in evict_inodes

On Mon, Jul 11, 2016 at 05:15:04PM -0700, Chunwei Chen wrote:
> We need to check i_count again with i_lock held, because iput might re-add
> i_count when lazytime is on. Without this check, we could end up with
> double-free or use-after-free.

Details, please.  Ideally - with a reproducer.  Who is calling that iput()
at that point of generic_shutdown_super() (has to be another thread) and
just what will happen if the same iput() is delayed until *after*
evict_inodes(), all the way into ->put_super().  At which point there's
no promise whatsoever that the data structures used by ->evict_inode()
hadn't been already freed...