From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
Greg Ungerer <gerg@linux-m68k.org>, Rob Landley <rob@landley.net>,
Bernd Edlinger <bernd.edlinger@hotmail.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Alexey Dobriyan <adobriyan@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Casey Schaufler <casey@schaufler-ca.com>,
LSM List <linux-security-module@vger.kernel.org>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH 3/5] exec: Remove recursion from search_binary_handler
Date: Tue, 12 May 2020 12:25:24 -0700 [thread overview]
Message-ID: <202005121218.ED0B728DA@keescook> (raw)
In-Reply-To: <874kslq9jm.fsf@x220.int.ebiederm.org>
On Tue, May 12, 2020 at 01:42:53PM -0500, Eric W. Biederman wrote:
> Kees Cook <keescook@chromium.org> writes:
> > Should binfmt_misc do the install, or can the consuming binfmt do it?
> > i.e. when binfmt_elf sees bprm->execfd, does it perform the install
> > instead?
>
> I am still thinking about this one, but here is where I am at. At a
> practical level passing the file descriptor of the script to interpreter
> seems like something we should encourage in the long term. It removes
> races and it is cheaper because then the interpreter does not have to
> turn around and open the script itself.
Yeah, this does sounds pretty good, though I have concerns about doing
it for a process that isn't expecting it. I've seen a lot of bad code
make assumptions about initial fd numbers. :(
> Strictly speaking binfmt_misc should not need to close the file
> descriptor in binfmt_misc because we have already unshared the files
> struct and reset_files_struct should handle restoring it.
If I get what you mean, I agree. The error case is fine.
> Calling fd_install in binfmt_misc still seems wrong, as that exposes
> the new file descriptor to user space with the old creds.
I haven't dug into the details here -- is there a real risk here? The
old creds are what opened the file originally for the exec. Are you
thinking about executable-but-not-readable files?
> It is possible although unlikely for userspace to find the file
> descriptor without consulting AT_EXECFD so just to be conservative I
> think we should install the file descriptor in begin_new_exec even if
> the next interpreter does not support AT_EXECFD.
I think universally installing the fd needs to be a distinct patch --
it's going to have a lot of consequences, IMO. We can certainly deal
with them, but I don't think it should be part of this clean-up series.
> I am still working on how to handle recursive binfmts but I suspect it
> is just a matter of having an array of struct files in struct
> linux_binprm.
If install is left if binfmt_misc, then the recursive problem goes away,
yes?
--
Kees Cook
next prev parent reply other threads:[~2020-05-12 19:25 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87h7wujhmz.fsf@x220.int.ebiederm.org>
[not found] ` <87sgga6ze4.fsf@x220.int.ebiederm.org>
2020-05-09 19:40 ` [PATCH 0/5] exec: Control flow simplifications Eric W. Biederman
2020-05-09 19:40 ` [PATCH 1/5] exec: Call cap_bprm_set_creds directly from prepare_binprm Eric W. Biederman
2020-05-09 20:04 ` Linus Torvalds
2020-05-09 19:41 ` [PATCH 2/5] exec: Directly call security_bprm_set_creds from __do_execve_file Eric W. Biederman
2020-05-09 20:07 ` Linus Torvalds
2020-05-09 20:12 ` Eric W. Biederman
2020-05-09 20:19 ` Linus Torvalds
2020-05-11 3:15 ` Kees Cook
2020-05-11 16:52 ` Eric W. Biederman
2020-05-11 21:18 ` Kees Cook
2020-05-09 19:41 ` [PATCH 3/5] exec: Remove recursion from search_binary_handler Eric W. Biederman
2020-05-09 20:16 ` Linus Torvalds
2020-05-10 4:22 ` Tetsuo Handa
2020-05-10 19:38 ` Linus Torvalds
2020-05-11 14:33 ` Eric W. Biederman
2020-05-11 19:10 ` Rob Landley
2020-05-13 21:59 ` Eric W. Biederman
2020-05-14 18:46 ` Rob Landley
2020-05-11 21:55 ` Kees Cook
2020-05-12 18:42 ` Eric W. Biederman
2020-05-12 19:25 ` Kees Cook [this message]
2020-05-12 20:31 ` Eric W. Biederman
2020-05-12 23:08 ` Kees Cook
2020-05-12 23:47 ` Kees Cook
2020-05-12 23:51 ` Kees Cook
2020-05-14 14:56 ` Eric W. Biederman
2020-05-14 16:56 ` Casey Schaufler
2020-05-14 17:02 ` Eric W. Biederman
2020-05-13 0:20 ` Linus Torvalds
2020-05-13 2:39 ` Rob Landley
2020-05-13 19:51 ` Linus Torvalds
2020-05-14 16:49 ` Eric W. Biederman
2020-05-09 19:42 ` [PATCH 4/5] exec: Allow load_misc_binary to call prepare_binfmt unconditionally Eric W. Biederman
2020-05-11 22:09 ` Kees Cook
2020-05-09 19:42 ` [PATCH 5/5] exec: Move the call of prepare_binprm into search_binary_handler Eric W. Biederman
2020-05-11 22:24 ` Kees Cook
2020-05-19 0:29 ` [PATCH v2 0/8] exec: Control flow simplifications Eric W. Biederman
2020-05-19 0:29 ` [PATCH v2 1/8] exec: Teach prepare_exec_creds how exec treats uids & gids Eric W. Biederman
2020-05-19 18:03 ` Kees Cook
2020-05-19 18:28 ` Linus Torvalds
2020-05-19 18:57 ` Eric W. Biederman
2020-05-19 0:30 ` [PATCH v2 2/8] exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds Eric W. Biederman
2020-05-19 15:34 ` Casey Schaufler
2020-05-19 18:10 ` Kees Cook
2020-05-19 21:28 ` James Morris
2020-05-19 0:31 ` [PATCH v2 3/8] exec: Convert security_bprm_set_creds into security_bprm_repopulate_creds Eric W. Biederman
2020-05-19 18:21 ` Kees Cook
2020-05-19 19:03 ` Eric W. Biederman
2020-05-19 19:14 ` Kees Cook
2020-05-20 20:22 ` Eric W. Biederman
2020-05-20 20:53 ` Kees Cook
2020-05-19 21:52 ` James Morris
2020-05-20 12:40 ` Eric W. Biederman
2020-05-19 0:31 ` [PATCH v2 4/8] exec: Allow load_misc_binary to call prepare_binfmt unconditionally Eric W. Biederman
2020-05-19 18:27 ` Kees Cook
2020-05-19 19:08 ` Eric W. Biederman
2020-05-19 19:17 ` Kees Cook
2020-05-19 0:32 ` [PATCH v2 5/8] exec: Move the call of prepare_binprm into search_binary_handler Eric W. Biederman
2020-05-19 18:27 ` Kees Cook
2020-05-19 21:30 ` James Morris
2020-05-19 0:33 ` [PATCH v2 6/8] exec/binfmt_script: Don't modify bprm->buf and then return -ENOEXEC Eric W. Biederman
2020-05-19 19:08 ` Kees Cook
2020-05-19 19:19 ` Eric W. Biederman
2020-05-19 0:33 ` [PATCH v2 7/8] exec: Generic execfd support Eric W. Biederman
2020-05-19 19:46 ` Kees Cook
2020-05-19 19:54 ` Linus Torvalds
2020-05-19 20:20 ` Eric W. Biederman
2020-05-19 21:59 ` Rob Landley
2020-05-20 16:05 ` Eric W. Biederman
2020-05-21 22:50 ` Rob Landley
2020-05-22 3:28 ` Eric W. Biederman
2020-05-22 4:51 ` Rob Landley
2020-05-22 13:35 ` Eric W. Biederman
2020-05-19 0:34 ` [PATCH v2 8/8] exec: Remove recursion from search_binary_handler Eric W. Biederman
2020-05-19 20:37 ` Kees Cook
2020-05-19 1:25 ` [PATCH v2 0/8] exec: Control flow simplifications Linus Torvalds
2020-05-19 21:55 ` Kees Cook
2020-05-20 13:02 ` Eric W. Biederman
2020-05-20 22:12 ` Eric W. Biederman
2020-05-20 23:43 ` Kees Cook
2020-05-21 11:53 ` Eric W. Biederman
2020-05-28 15:38 ` [PATCH 0/11] exec: cred calculation simplifications Eric W. Biederman
2020-05-28 15:41 ` [PATCH 01/11] exec: Reduce bprm->per_clear to a single bit Eric W. Biederman
2020-05-28 19:04 ` Linus Torvalds
2020-05-28 19:17 ` Eric W. Biederman
2020-05-28 15:42 ` [PATCH 02/11] exec: Introduce active_per_clear the per file version of per_clear Eric W. Biederman
2020-05-28 19:05 ` Linus Torvalds
2020-05-28 15:42 ` [PATCH 03/11] exec: Compute file based creds only once Eric W. Biederman
2020-05-28 15:43 ` [PATCH 04/11] exec: Move uid/gid handling from creds_from_file into bprm_fill_uid Eric W. Biederman
2020-05-28 15:44 ` Eric W. Biederman
2020-05-28 15:44 ` [PATCH 05/11] exec: In bprm_fill_uid use CAP_SETGID to see if a gid change is safe Eric W. Biederman
2020-05-28 15:48 ` [PATCH 06/11] exec: Don't set secureexec when the uid or gid changes are abandoned Eric W. Biederman
2020-05-28 15:48 ` [PATCH 07/11] exec: Set saved, fs, and effective ids together in bprm_fill_uid Eric W. Biederman
2020-05-28 15:49 ` [PATCH 08/11] exec: In bprm_fill_uid remove unnecessary no new privs check Eric W. Biederman
2020-05-28 15:49 ` [PATCH 09/11] exec: In bprm_fill_uid only set per_clear when honoring suid or sgid Eric W. Biederman
2020-05-28 19:08 ` Linus Torvalds
2020-05-28 19:21 ` Eric W. Biederman
2020-05-28 15:50 ` [PATCH 10/11] exec: In bprm_fill_uid set secureexec at same time as per_clear Eric W. Biederman
2020-05-28 15:50 ` [PATCH 11/11] exec: Remove the label after_setid from bprm_fill_uid Eric W. Biederman
2020-05-29 16:45 ` [PATCH 0/2] exec: Remove the computation of bprm->cred Eric W. Biederman
2020-05-29 16:46 ` [PATCH 1/2] exec: Add a per bprm->file version of per_clear Eric W. Biederman
2020-05-29 21:06 ` Kees Cook
2020-05-30 3:23 ` Eric W. Biederman
2020-05-30 5:14 ` Kees Cook
2020-05-29 16:47 ` [PATCH 2/2] exec: Compute file based creds only once Eric W. Biederman
2020-05-29 21:24 ` Kees Cook
2020-05-30 3:28 ` Eric W. Biederman
2020-05-30 5:18 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=202005121218.ED0B728DA@keescook \
--to=keescook@chromium.org \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=bernd.edlinger@hotmail.de \
--cc=casey@schaufler-ca.com \
--cc=ebiederm@xmission.com \
--cc=gerg@linux-m68k.org \
--cc=jannh@google.com \
--cc=jmorris@namei.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=oleg@redhat.com \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=rob@landley.net \
--cc=serge@hallyn.com \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).