linux-kernel - Re: [PATCH v5 bpf-next 1/5] namei: Introduce new helper function path_walk

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: <ob35gal3xcbkdkcdpekyvglwg5jsf6sgkdeyoj3gu4jr76ilxh@yhupo3iwet3l>
Date: Wed, 25 Jun 2025 12:30:34 +0200
From: Jan Kara <jack@...e.cz>
To: Song Liu <song@...nel.org>
Cc: Jan Kara <jack@...e.cz>, bpf@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, kernel-team@...a.com, andrii@...nel.org, eddyz87@...il.com, 
	ast@...nel.org, daniel@...earbox.net, martin.lau@...ux.dev, 
	viro@...iv.linux.org.uk, brauner@...nel.org, kpsingh@...nel.org, mattbobrowski@...gle.com, 
	m@...wtm.org, neil@...wn.name
Subject: Re: [PATCH v5 bpf-next 1/5] namei: Introduce new helper function
 path_walk_parent()

On Tue 24-06-25 10:37:36, Song Liu wrote:
> On Tue, Jun 24, 2025 at 5:18 AM Jan Kara <jack@...e.cz> wrote:
> > > + *
> > > + * Returns: either an ERR_PTR() or the chosen parent which will have had
> > > + * the refcount incremented.
> > > + */
> >
> > The behavior with LOOKUP_NO_XDEV is kind of odd (not your fault) and
> > interestingly I wasn't able to find a place that would depend on the path
> > being updated in that case. So either I'm missing some subtle detail (quite
> > possible) or we can clean that up in the future.
> 
> We have RESOLVE_NO_XDEV in uapi/linux/openat2.h, so I guess we
> cannot really remove it?

I didn't mean to remove the LOOKUP_NO_XDEV flag, I meant to not update the
passed path if LOOKUP_NO_XDEV is set, we are crossing the mountpoint and
thus returning -EXDEV. As far as I've checked once we return error,
everybody just path_put()s the nd->path so its update is just pointless.
But there are many (indirect) callers so I might have missed some case.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR