From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Linux API <linux-api@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Linux Security Module <linux-security-module@vger.kernel.org>,
Akinobu Mita <akinobu.mita@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Alexey Dobriyan <adobriyan@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Daniel Micay <danielmicay@gmail.com>,
Djalal Harouni <tixxdz@gmail.com>,
"Dmitry V . Levin" <ldv@altlinux.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@kernel.org>,
"J . Bruce Fields" <bfields@fieldses.org>,
Jeff Layton <jlayton@poochiereds.net>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Oleg Nesterov <oleg@redhat.com>,
Solar Designer <solar@openwall.com>,
Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH v7 07/11] proc: flush task dcache entries from all procfs instances
Date: Sat, 25 Jan 2020 10:45:25 -0800 [thread overview]
Message-ID: <CAHk-=wiGNSQCA8TYa1Akp0_GRpe=ELKDPkDX5nzM5R=oDy1U+Q@mail.gmail.com> (raw)
In-Reply-To: <20200125130541.450409-8-gladkov.alexey@gmail.com>
On Sat, Jan 25, 2020 at 5:06 AM Alexey Gladkov <gladkov.alexey@gmail.com> wrote:
>
> This allows to flush dcache entries of a task on multiple procfs mounts
> per pid namespace.
From a quick read-through, this is the only one I really react negatively to.
The locking looks odd. It only seems to protect the new proc_mounts
list, but then it's a whole big rwsem, and it's taken over all of
proc_flush_task_mnt(), and the locking is exported to all over as a
result of that - including the dummy functions for "there is no proc"
case.
And proc_flush_task_mnt() itself should need no locking over any of
it, so it's all just for the silly looping over the list.
So
(a) this looks fishy and feels wrong - I get a very strong feeling
that the locking is wrong to begin with, and could/should have been
done differently
(b) all the locking should have been internal to /proc, and those
wrappers shouldn't exist in a common header file (and certainly not
for the non-proc case).
Yes, (a) is just a feeling, and I don't have any great suggestions.
Maybe make it an RCU list and use a spinlock for updating it?
But (b) is pretty much a non-starter in this form. Those wrappers
shouldn't be in a globally exported core header file. No way.
Linus
next prev parent reply other threads:[~2020-01-25 18:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-25 13:05 [PATCH v7 00/11] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 01/11] proc: Rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 02/11] proc: add proc_fs_info struct to store proc information Alexey Gladkov
2020-01-28 13:43 ` Oleg Nesterov
2020-01-28 14:58 ` Oleg Nesterov
2020-01-25 13:05 ` [PATCH v7 03/11] proc: move /proc/{self|thread-self} dentries to proc_fs_info Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 04/11] proc: move hide_pid, pid_gid from pid_namespace " Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 05/11] proc: add helpers to set and get proc hidepid and gid mount options Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 06/11] proc: support mounting procfs instances inside same pid namespace Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 07/11] proc: flush task dcache entries from all procfs instances Alexey Gladkov
2020-01-25 18:45 ` Linus Torvalds [this message]
2020-01-27 23:23 ` Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 09/11] proc: add option to mount only a pids subset Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 10/11] docs: proc: add documentation for "hidepid=4" and "subset=pidfs" options and new mount behavior Alexey Gladkov
2020-01-25 13:05 ` [PATCH v7 11/11] proc: Move hidepid values to uapi as they are user interface to mount Alexey Gladkov
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