From: Al Viro <viro@zeniv.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: 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 13:37:40 +0000 [thread overview]
Message-ID: <YguspMvu6M6NJ1hL@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <CAJfpegvVKWHhhXwOi9jDUOJi2BnYSDxZQrp1_RRrpVjjZ3Rs2w@mail.gmail.com>
On Tue, Feb 15, 2022 at 10:56:29AM +0100, Miklos Szeredi wrote:
> Doing "lock_rename() + lookup last components" would fix this race.
No go - thanks to the possibility of AT_SYMLINK_FOLLOW there.
Think of it - we'd need to
* lock parents (both at the same time)
* look up the last component of source
* if it turns a symlink - unlock parents and repeat the entire
thing for its body, except when asked not to.
* when we are done with the source, look the last component of
target up
... and then there is sodding -ESTALE handling, with all the elegance
that brings in.
> If this was only done on retry, then that would prevent possible
> performance regressions, at the cost of extra complexity.
Extra compared to the above, that is. How delightful...
next prev parent reply other threads:[~2022-02-15 13:37 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 [this message]
2022-02-15 16:06 ` Al Viro
2022-02-15 16:17 ` Matthew Wilcox
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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