From: Rich Felker <dalias@libc.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fw@deneb.enyo.de>,
"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
Subject: Re: XFS reports lchmod failure, but changes file system contents
Date: Wed, 12 Feb 2020 14:55:43 -0500 [thread overview]
Message-ID: <20200212195543.GA1663@brightrain.aerifal.cx> (raw)
In-Reply-To: <20200212195118.GN23230@ZenIV.linux.org.uk>
On Wed, Feb 12, 2020 at 07:51:18PM +0000, Al Viro wrote:
> 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?
Indeed, my expectation was that both fchmod and chmod via the magic
symlink succeed, given a new enough kernel for operations on O_PATH
fds to be supported. I'd like to switch to using fstat+fchmod to do
this, and only fallback to /proc on older kernels where O_PATH fds
cause EBADF. But I'm somewhat concerned by the inconsistency between
behavior of the two approaches.
Rich
next prev parent reply other threads:[~2020-02-12 19:58 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 [this message]
2020-02-12 20:01 ` Florian Weimer
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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