From: ebiederm@xmission.com (Eric W. Biederman)
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: 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>,
Kees Cook <keescook@chromium.org>,
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: Mon, 11 May 2020 09:33:21 -0500 [thread overview]
Message-ID: <87sgg6v8we.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <CAHk-=wgQ2ovXMW=5ZHCpowkE1PwPQSL7oV4YXzBxd6eqNRXxnQ@mail.gmail.com> (Linus Torvalds's message of "Sun, 10 May 2020 12:38:20 -0700")
Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Sat, May 9, 2020 at 9:30 PM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
>>
>> Wouldn't this change cause
>>
>> if (fd_binary > 0)
>> ksys_close(fd_binary);
>> bprm->interp_flags = 0;
>> bprm->interp_data = 0;
>>
>> not to be called when "Search for the interpreter" failed?
>
> Good catch. We seem to have some subtle magic wrt the fd_binary file
> descriptor, which depends on the recursive behavior.
Yes. I Tetsuo I really appreciate you noticing this. This is exactly
the kind of behavior I am trying to flush out and keep from being
hidden.
> I'm not seeing how to fix it cleanly with the "turn it into a loop".
> Basically, that binfmt_misc use-case isn't really a tail-call.
I have reservations about installing a new file descriptor before
we process the close on exec logic and the related security modules
closing file descriptors that your new credentials no longer give
you access to logic.
I haven't yet figured out how opening a file descriptor during exec
should fit into all of that.
What I do see is that interp_data is just a parameter that is smuggled
into the call of search binary handler. And the next binary handler
needs to be binfmt_elf for it to make much sense, as only binfmt_elf
(and binfmt_elf_fdpic) deals with BINPRM_FLAGS_EXECFD.
So I think what needs to happen is to rename bprm->interp_data to
bprm->execfd, remove BINPRM_FLAGS_EXECFD and make closing that file
descriptor free_bprm's responsiblity.
I hope such a change will make it easier to see all of the pieces that
are intereacting during exec.
I am still asking: is the installation of that file descriptor useful if
it is not exported passed to userspace as an AT_EXECFD note?
I will dig in and see what I can come up with.
Eric
next prev parent reply other threads:[~2020-05-11 14:37 UTC|newest]
Thread overview: 149+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 19:39 exec: Promised cleanups after introducing exec_update_mutex Eric W. Biederman
2020-05-05 19:41 ` [PATCH 1/7] binfmt: Move install_exec_creds after setup_new_exec to match binfmt_elf Eric W. Biederman
2020-05-05 20:45 ` Kees Cook
2020-05-06 12:42 ` Greg Ungerer
2020-05-06 12:56 ` Eric W. Biederman
2020-05-05 19:41 ` [PATCH 2/7] exec: Make unlocking exec_update_mutex explict Eric W. Biederman
2020-05-05 20:46 ` Kees Cook
2020-05-05 19:42 ` [PATCH 3/7] exec: Rename the flag called_exec_mmap point_of_no_return Eric W. Biederman
2020-05-05 20:49 ` Kees Cook
2020-05-05 19:43 ` [PATCH 4/7] exec: Merge install_exec_creds into setup_new_exec Eric W. Biederman
2020-05-05 20:50 ` Kees Cook
2020-05-05 19:44 ` [PATCH 5/7] exec: In setup_new_exec cache current in the local variable me Eric W. Biederman
2020-05-05 20:51 ` Kees Cook
2020-05-05 19:45 ` [PATCH 6/7] exec: Move most of setup_new_exec into flush_old_exec Eric W. Biederman
2020-05-05 21:29 ` Kees Cook
2020-05-06 14:57 ` Eric W. Biederman
2020-05-06 15:30 ` Kees Cook
2020-05-07 19:51 ` Eric W. Biederman
2020-05-07 21:51 ` Eric W. Biederman
2020-05-08 5:50 ` Kees Cook
2020-05-05 19:46 ` [PATCH 7/7] exec: Rename flush_old_exec begin_new_exec Eric W. Biederman
2020-05-05 21:30 ` Kees Cook
2020-05-06 12:41 ` exec: Promised cleanups after introducing exec_update_mutex Greg Ungerer
2020-05-08 18:43 ` [PATCH 0/6] exec: Trivial cleanups for exec Eric W. Biederman
2020-05-08 18:44 ` [PATCH 1/6] exec: Move the comment from above de_thread to above unshare_sighand Eric W. Biederman
2020-05-09 5:02 ` Kees Cook
2020-05-08 18:44 ` [PATCH 2/6] exec: Fix spelling of search_binary_handler in a comment Eric W. Biederman
2020-05-09 5:03 ` Kees Cook
2020-05-08 18:45 ` [PATCH 3/6] exec: Stop open coding mutex_lock_killable of cred_guard_mutex Eric W. Biederman
2020-05-09 5:08 ` Kees Cook
2020-05-09 19:18 ` Linus Torvalds
2020-05-09 19:57 ` Eric W. Biederman
2020-05-10 20:33 ` Kees Cook
2020-05-08 18:45 ` [PATCH 4/6] exec: Run sync_mm_rss before taking exec_update_mutex Eric W. Biederman
2020-05-09 5:15 ` Kees Cook
2020-05-09 14:17 ` Eric W. Biederman
2020-05-08 18:47 ` [PATCH 5/6] exec: Move handling of the point of no return to the top level Eric W. Biederman
2020-05-09 5:31 ` Kees Cook
2020-05-09 13:39 ` Eric W. Biederman
2020-05-08 18:48 ` [PATCH 6/6] exec: Set the point of no return sooner Eric W. Biederman
2020-05-09 5:33 ` Kees Cook
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 [this message]
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
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
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