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From: Andy Lutomirski <luto@kernel.org>
To: David Howells <dhowells@redhat.com>, Jann Horn <jannh@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Casey Schaufler <casey@schaufler-ca.com>,
	raven@themaw.net, Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	linux-block@vger.kernel.org, keyrings@vger.kernel.org,
	LSM List <linux-security-module@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/8] security: Override creds in __fput() with last fputter's creds [ver #2]
Date: Tue, 4 Jun 2019 11:15:14 -0700
Message-ID: <CALCETrXLoowmrHHWWr3OqsOGBkyGsV_x0nADaEyv+_ysGQdM3g@mail.gmail.com> (raw)
In-Reply-To: <155966611030.17449.1411028213562548153.stgit@warthog.procyon.org.uk>

On Tue, Jun 4, 2019 at 9:35 AM David Howells <dhowells@redhat.com> wrote:
>
> So that the LSM can see the credentials of the last process to do an fput()
> on a file object when the file object is being dismantled, do the following
> steps:
>
>  (1) Cache the current credentials in file->f_fput_cred at the point the
>      file object's reference count reaches zero.

I don't think it's valid to capture credentials in close().  This
sounds very easy to spoof, especially when you consider that you can
stick an fd in unix socket and aim it at a service that's just going
to ignore it and close it.

IOW I think this is at least as invalid as looking at current_cred()
in write(), which is a classic bug that gets repeated regularly.

--Andy

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-04 16:34 [RFC][PATCH 0/8] Mount, FS, Block and Keyrings notifications " David Howells
2019-06-04 16:35 ` [PATCH 1/8] security: Override creds in __fput() with last fputter's creds " David Howells
2019-06-04 18:15   ` Andy Lutomirski [this message]
2019-06-04 16:35 ` [PATCH 2/8] General notification queue with user mmap()'able ring buffer " David Howells
2019-06-04 16:35 ` [PATCH 3/8] keys: Add a notification facility " David Howells
2019-06-04 16:35 ` [PATCH 4/8] vfs: Add a mount-notification " David Howells
2019-06-04 16:35 ` [PATCH 5/8] vfs: Add superblock notifications " David Howells
2019-06-04 16:36 ` [PATCH 6/8] fsinfo: Export superblock notification counter " David Howells
2019-06-04 16:36 ` [PATCH 7/8] block: Add block layer notifications " David Howells
2019-06-04 16:36 ` [PATCH 8/8] Add sample notification program " David Howells
2019-06-04 17:43 ` [RFC][PATCH 0/8] Mount, FS, Block and Keyrings notifications " Andy Lutomirski
2019-06-04 20:31   ` Casey Schaufler
2019-06-04 21:05     ` Andy Lutomirski
2019-06-04 22:03       ` Casey Schaufler
2019-06-05  8:41   ` David Howells
2019-06-05 14:50     ` Casey Schaufler
2019-06-05 16:04       ` Andy Lutomirski
2019-06-05 17:01         ` Casey Schaufler
2019-06-05 17:47           ` Andy Lutomirski
2019-06-05 18:12             ` Casey Schaufler
2019-06-05 18:25             ` Stephen Smalley
2019-06-05 19:28               ` Greg KH
2019-06-05 21:01                 ` Stephen Smalley
2019-06-05 16:56     ` Rational model for UID based controls David Howells
2019-06-05 17:40       ` Casey Schaufler
2019-06-05 21:06       ` David Howells
2019-06-05 17:21     ` [RFC][PATCH 0/8] Mount, FS, Block and Keyrings notifications [ver #2] David Howells
2019-06-04 20:39 ` David Howells
2019-06-04 20:57   ` Andy Lutomirski
     [not found]     ` <CAB9W1A0AgMYOwGx9c-TmAt=1O6Bjsr2P3Nhd=2+QV39dgw0CrA@mail.gmail.com>
2019-06-05  4:19       ` Andy Lutomirski
2019-06-05 13:47         ` Stephen Smalley
2019-06-04 21:11   ` Casey Schaufler

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