linux-kernel - Re: fs: lockup on rename

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] [day] [month] [year] [list]

Date:	Sun, 26 Oct 2014 23:42:30 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: fs: lockup on rename_mutex in fs/dcache.c:1035

On Sun, Oct 26, 2014 at 04:33:11PM -0700, Linus Torvalds wrote:
> On Sun, Oct 26, 2014 at 2:57 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> >  .. snip ..
> > in d_walk(), __list_del() instead of list_del() in __dentry_kill(), d_u.d_child
> > turning into d_child everywhere, while d_alias turns into d_u.d_alias...
> >
> > It looks like that way we would get no retries on the second pass.  Comments?
> 
> Since I missed the whole issue with d_child.next, I'm not sure any
> comments from me would be helpful.
> 
> It does sound like trying to be more careful with d_child and using
> d_alias instead is a good idea. d_alias is only used under the dentry
> lock, and not in any horribly subtle situations, right? So that sounds
> like a good change regardless of this particular fix - making the
> union happen in a less nasty place..

OK...  See vfs.git#experimental-d_walk - the first commit there moves
d_rcu from d_child to d_alias, the second is basically "skip the killed
siblings rather than restarting the tree walk".
--
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/