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From: Andy Lutomirski <>
Cc: Aleksa Sarai <>,
	Al Viro <>,
	Jeff Layton <>,
	"J. Bruce Fields" <>,
	Arnd Bergmann <>,
	David Howells <>,
	"Eric W. Biederman" <>,
	Christian Brauner <>,
	Linux API <>,
	Andrew Lutomirski <>, Jann Horn <>,
	David Drysdale <>,
	Aleksa Sarai <>,
	Linux Containers <>,
	Linux FS Devel <>,
	LKML <>,
	linux-arch <>
Subject: Re: [PATCH v4 2/4] namei: O_BENEATH-style path resolution flags
Date: Fri, 23 Nov 2018 08:07:03 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

> On Nov 23, 2018, at 5:10 AM, Jürg Billeter <> wrote:
> Hi Aleksa,
>> On Tue, 2018-11-13 at 01:26 +1100, Aleksa Sarai wrote:
>> * O_BENEATH: Disallow "escapes" from the starting point of the
>>  filesystem tree during resolution (you must stay "beneath" the
>>  starting point at all times). Currently this is done by disallowing
>>  ".." and absolute paths (either in the given path or found during
>>  symlink resolution) entirely, as well as all "magic link" jumping.
> With open_tree(2) and OPEN_TREE_CLONE, will O_BENEATH still be
> necessary?

This discussion reminds me of something I’m uncomfortable with in the
current patches: currently, most of the O_ flags determine some
property of the returned opened file.  The new O_ flags you're adding
don't -- instead, they affect the lookup of the file.  So O_BENEATH
doesn't return a descriptor that can only be used to loop up files
beneath it -- it just controls whether open(2) succeeds or fails.  It
might be nice for the naming of the flags to reflect this.  I also
don't love that we have some magic AT_ flags that work with some
syscalls and some magic O_ flags that work with others.

In this regard, I liked the AT_ naming better.  Although I don't love
adding AT_ flags because the restrict our ability to usefully use the
high bits of the fd in the future.


  reply	other threads:[~2018-11-23 16:07 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-12 14:26 [PATCH v4 0/4] namei: O_* flags to restrict path resolution Aleksa Sarai
2018-11-12 14:26 ` [PATCH v4 1/4] namei: split out nd->dfd handling to dirfd_path_init Aleksa Sarai
2018-11-12 14:26 ` [PATCH v4 2/4] namei: O_BENEATH-style path resolution flags Aleksa Sarai
2018-11-23 12:10   ` Jürg Billeter
2018-11-23 16:07     ` Andy Lutomirski [this message]
2018-11-23 16:48       ` Aleksa Sarai
2018-11-23 16:52         ` Aleksa Sarai
2018-11-23 16:58     ` Aleksa Sarai
2018-11-12 14:26 ` [PATCH v4 3/4] namei: O_THISROOT: chroot-like path resolution Aleksa Sarai
2018-11-12 14:26 ` [PATCH v4 4/4] namei: aggressively check for nd->root escape on ".." resolution Aleksa Sarai

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