linux-kernel - RE: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD

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: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f712a5551ebd4626acd17ac80fe51879@AcuMS.aculab.com>
Date:   Fri, 23 Jun 2023 13:10:26 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Matthew Wilcox' <willy@...radead.org>, stsp <stsp2@...dex.ru>
CC:     Jeff Layton <jlayton@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD_GETLK

From: Matthew Wilcox
> Sent: 20 June 2023 14:46
> 
> On Tue, Jun 20, 2023 at 06:39:07PM +0500, stsp wrote:
> > Though it will, for sure, represent the
> > task that _owns_ the lock.
> 
> No, it *DOESN'T*.  I can open a file, SCM_RIGHTS pass it to another task
> and then exit.  Now the only owner of that lock is the recipient ...
> who may not even have received the fd yet.

Do these locks persist across fork+exec?

What happens is a completely unrelated process opens /proc/<pid>/fd
while a lock is held and then the (nominally) lock-holding
process closes the fd (or exits).

While it might be a useful diagnostic to know the pid of the
process that acquired the lock it clearly has no relationship
with any process that currently has an fd[] table entry that
references the file.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)