From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jeff Layton <jlayton@kernel.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
"J. Bruce Fields" <bfields@fieldses.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Daniel P . Berrangé" <berrange@redhat.com>,
"Kate Stewart" <kstewart@linuxfoundation.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Philippe Ombredanne" <pombredanne@nexb.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] locks: change POSIX lock ownership on execve when files_struct is displaced
Date: Sat, 17 Mar 2018 15:05:34 +0000 [thread overview]
Message-ID: <20180317150533.GM30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180317142520.30520-1-jlayton@kernel.org>
On Sat, Mar 17, 2018 at 10:25:20AM -0400, Jeff Layton wrote:
> From: Jeff Layton <jlayton@redhat.com>
>
> POSIX mandates that open fds and their associated file locks should be
> preserved across an execve. This works, unless the process is
> multithreaded at the time that execve is called.
>
> In that case, we'll end up unsharing the files_struct but the locks will
> still have their fl_owner set to the address of the old one. Eventually,
> when the other threads die and the last reference to the old
> files_struct is put, any POSIX locks get torn down since it looks like
> a close occurred on them.
>
> The result is that all of your open files will be intact with none of
> the locks you held before execve. The simple answer to this is "use OFD
> locks", but this is a nasty surprise and it violates the spec.
>
> On a successful execve, change ownership of any POSIX file_locks
> associated with the old files_struct to the new one, if we ended up
> swapping it out.
TBH, I don't like the way you implement that. Why not simply use
iterate_fd()?
next prev parent reply other threads:[~2018-03-17 15:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-17 14:25 [PATCH] locks: change POSIX lock ownership on execve when files_struct is displaced Jeff Layton
2018-03-17 15:05 ` Al Viro [this message]
2018-03-17 15:43 ` Jeff Layton
2018-03-17 15:52 ` Al Viro
2018-03-17 19:28 ` Jeff Layton
2018-03-17 16:58 ` [PATCH v2] " Jeff Layton
[not found] ` <87bmfgvg8w.fsf@xmission.com>
2018-03-22 11:14 ` Al Viro
[not found] ` <871sgcvfh7.fsf@xmission.com>
2018-03-22 10:57 ` Jeff Layton
2018-04-02 12:56 ` Jeff Layton
2018-04-03 17:22 ` Eric W. Biederman
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