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From: Florian Weimer <fw@deneb.enyo.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
	Christoph Hellwig <hch@infradead.org>,
	linux-xfs@vger.kernel.org, libc-alpha@sourceware.org,
	linux-fsdevel@vger.kernel.org, Rich Felker <dalias@libc.org>
Subject: Re: XFS reports lchmod failure, but changes file system contents
Date: Wed, 12 Feb 2020 21:01:22 +0100	[thread overview]
Message-ID: <87wo8rlgml.fsf@mid.deneb.enyo.de> (raw)
In-Reply-To: <20200212195118.GN23230@ZenIV.linux.org.uk> (Al Viro's message of "Wed, 12 Feb 2020 19:51:18 +0000")

* Al Viro:

> On Wed, Feb 12, 2020 at 08:15:08PM +0100, Florian Weimer wrote:
>
>> | Further, I've found some inconsistent behavior with ext4: chmod on the
>> | magic symlink fails with EOPNOTSUPP as in Florian's test, but fchmod
>> | on the O_PATH fd succeeds and changes the symlink mode. This is with
>> | 5.4. Cany anyone else confirm this? Is it a problem?
>> 
>> It looks broken to me because fchmod (as an inode-changing operation)
>> is not supposed to work on O_PATH descriptors.
>
> Why?  O_PATH does have an associated inode just fine; where does
> that "not supposed to" come from?

It fails on most file systems right now.  I thought that was expected.
Other system calls (fsetxattr IIRC) do not work on O_PATH descriptors,
either.  I assumed that an O_PATH descriptor was not intending to
confer that capability.  Even openat fails.

Although fchmod does succeed on read-only descriptors, which is a bit
strange.

  parent reply	other threads:[~2020-02-12 20:02 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 11:48 XFS reports lchmod failure, but changes file system contents Florian Weimer
2020-02-12 12:15 ` Florian Weimer
2020-02-12 16:16 ` Darrick J. Wong
2020-02-12 18:11   ` Christoph Hellwig
2020-02-12 18:37     ` Darrick J. Wong
2020-02-12 19:15       ` Florian Weimer
2020-02-12 19:51         ` Al Viro
2020-02-12 19:55           ` Rich Felker
2020-02-12 20:01           ` Florian Weimer [this message]
2020-02-12 20:17             ` Andreas Schwab
2020-02-12 20:19               ` Rich Felker
2020-02-12 20:26                 ` Florian Weimer
2020-02-12 20:38                   ` Rich Felker
2020-02-12 20:27                 ` Al Viro
2020-02-12 20:36                   ` Rich Felker
2020-02-12 20:18             ` Rich Felker
2020-02-12 20:38             ` Paul Eggert
2020-02-21  4:09             ` Aleksa Sarai
2020-02-21  5:02               ` Al Viro
2020-02-21  5:21                 ` Aleksa Sarai
2020-02-12 18:50     ` Florian Weimer
2020-02-12 18:55       ` Christoph Hellwig

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