From: Al Viro <viro@zeniv.linux.org.uk>
To: Andy Lutomirski <luto@amacapital.net>
Cc: stsp <stsp2@yandex.ru>,
linux-kernel@vger.kernel.org,
"Stefan Metzmacher" <metze@samba.org>,
"Eric Biederman" <ebiederm@xmission.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Christian Brauner" <brauner@kernel.org>,
"Jan Kara" <jack@suse.cz>, "Jeff Layton" <jlayton@kernel.org>,
"Chuck Lever" <chuck.lever@oracle.com>,
"Alexander Aring" <alex.aring@gmail.com>,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Christian Göttsche" <cgzones@googlemail.com>,
"Aleksa Sarai" <cyphar@cyphar.com>
Subject: Re: [PATCH v2 0/2] implement OA2_INHERIT_CRED flag for openat2()
Date: Thu, 25 Apr 2024 02:43:58 +0100 [thread overview]
Message-ID: <20240425014358.GG2118490@ZenIV> (raw)
In-Reply-To: <CALCETrWswr5jAzD9BkdCqLX=d8vReO8O9dVmZfL7HXdvwkft9g@mail.gmail.com>
On Wed, Apr 24, 2024 at 05:43:02PM -0700, Andy Lutomirski wrote:
> I like that, but you're blocking it the wrong way. My concern is that
> someone does dfd = open("/proc/PID/fd/3") and then openat(dfd, ...,
> OA2_INHERIT_CRED); IIRC open("/proc/PID/fd/3") is extremely magical
> and returns the _same open file description_ (struct file) as PID's fd
> 3.
No, it doesn't. We could implement that, but if we do that'll be
*not* a part of procfs and it's going to be limited to current task
only.
There are two different variants of /dev/fd/* semantics - one is
"opening /dev/fd/42 is an equivalent of dup(42)", another is
"opening /dev/fd/42 is an equivalent of opening the same fs object
that is currently accessed via descriptor 42". Linux is doing the
latter, and we can't switch - that would break a lot of userland
software, including a lot of scripts.
I'm not saying I like the series, but this particular objection is bogus -
open via procfs symlinks is *not* an equivalent of dup() and that is not
going to change.
next prev parent reply other threads:[~2024-04-25 1:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-23 11:01 [PATCH v2 0/2] implement OA2_INHERIT_CRED flag for openat2() Stas Sergeev
2024-04-23 11:01 ` [PATCH 1/2] fs: reorganize path_openat() Stas Sergeev
2024-04-23 11:01 ` [PATCH 2/2] openat2: add OA2_INHERIT_CRED flag Stas Sergeev
2024-04-23 16:44 ` [PATCH v2 0/2] implement OA2_INHERIT_CRED flag for openat2() Andy Lutomirski
2024-04-23 18:05 ` stsp
2024-04-23 22:52 ` stsp
2024-04-24 10:57 ` stsp
2024-04-25 0:43 ` Andy Lutomirski
2024-04-25 1:43 ` Al Viro [this message]
2024-04-25 3:31 ` Andy Lutomirski
2024-04-25 11:02 ` stsp
[not found] <20240423104824.10464-1-stsp2@yandex.ru>
2024-04-23 10:58 ` Stefan Metzmacher
2024-04-23 11:02 ` stsp
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