From: Matthew Wilcox <willy@infradead.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Xavier Roche <xavier.roche@algolia.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: race between vfs_rename and do_linkat (mv and link)
Date: Tue, 15 Feb 2022 16:17:11 +0000 [thread overview]
Message-ID: <YgvSB6CKAhF5IXFj@casper.infradead.org> (raw)
In-Reply-To: <YgvPbljmJXsR7ESt@zeniv-ca.linux.org.uk>
On Tue, Feb 15, 2022 at 04:06:06PM +0000, Al Viro wrote:
> On Tue, Feb 15, 2022 at 01:37:40PM +0000, Al Viro wrote:
> > On Tue, Feb 15, 2022 at 10:56:29AM +0100, Miklos Szeredi wrote:
> >
> > > Doing "lock_rename() + lookup last components" would fix this race.
>
> "Fucking ugly" is inadequate for the likely results of that approach.
> It's guaranteed to be a source of headache for pretty much ever after.
>
> Does POSIX actually make any promises in that area? That would affect
> how high a cost we ought to pay for that - I agree that it would be nicer
> to have atomicity from userland point of view, but there's a difference
> between hard bug and QoI issue.
As I understand the original report, it relies on us hitting the nlink ==
0 at exactly the wrong moment. Can't we just restart the entire path
resolution if we find a target with nlink == 0? Sure, it's a lot of
extra work, but you've got to be trying hard to hit it in the first place.
next prev parent reply other threads:[~2022-02-15 16:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 21:07 fs: race between vfs_rename and do_linkat (mv and link) Xavier Roche
2022-02-15 9:56 ` Miklos Szeredi
2022-02-15 13:37 ` Al Viro
2022-02-15 16:06 ` Al Viro
2022-02-15 16:17 ` Matthew Wilcox [this message]
2022-02-15 16:20 ` Al Viro
2022-02-16 9:28 ` Miklos Szeredi
2022-02-16 10:28 ` Miklos Szeredi
2022-02-16 13:18 ` Xavier Roche
2022-02-16 13:37 ` Miklos Szeredi
2022-02-18 15:37 ` Miklos Szeredi
2022-02-15 16:18 ` Al Viro
2022-02-15 16:56 ` Xavier Roche
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