From: ebiederm@xmission.com (Eric W. Biederman)
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: linux-kernel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
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>,
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>,
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>,
Alexey Gladkov <gladkov.alexey@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jeff Dike <jdike@addtoit.com>,
Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>
Subject: Re: [PATCH 3/3] proc: Remove the now unnecessary internal mount of proc
Date: Fri, 28 Feb 2020 15:40:22 -0600 [thread overview]
Message-ID: <87eeuepf09.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200228203915.jelui3l5xue5utpx@wittgenstein> (Christian Brauner's message of "Fri, 28 Feb 2020 21:39:15 +0100")
Christian Brauner <christian.brauner@ubuntu.com> writes:
> On Fri, Feb 28, 2020 at 02:19:22PM -0600, Eric W. Biederman wrote:
>>
>> There remains no more code in the kernel using pids_ns->proc_mnt,
>> therefore remove it from the kernel.
>>
>> The big benefit of this change is that one of the most error prone and
>> tricky parts of the pid namespace implementation, maintaining kernel
>> mounts of proc is removed.
>>
>> In addition removing the unnecessary complexity of the kernel mount
>> fixes a regression that caused the proc mount options to be ignored.
>> Now that the initial mount of proc comes from userspace, those mount
>> options are again honored. This fixes Android's usage of the proc
>> hidepid option.
>>
>> Reported-by: Alistair Strachan <astrachan@google.com>
>> Fixes: e94591d0d90c ("proc: Convert proc_mount to use mount_ns.")
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>> ---
>> fs/proc/root.c | 36 -----------------------------------
>
> What about proc_flush_task()? Or is this on top of your other series?
On top of the other series. Which is why it is a reply to it.
That I have pushed into linux-next earlier today.
No one seems worried enough about that patchset to comment on v2 so I am
just going with it.
>> include/linux/pid_namespace.h | 2 --
>> include/linux/proc_ns.h | 5 -----
>> kernel/pid.c | 8 --------
>> kernel/pid_namespace.c | 7 -------
>> 5 files changed, 58 deletions(-)
>>
>> diff --git a/fs/proc/root.c b/fs/proc/root.c
>> index 608233dfd29c..2633f10446c3 100644
>> --- a/fs/proc/root.c
>> +++ b/fs/proc/root.c
>> @@ -292,39 +292,3 @@ struct proc_dir_entry proc_root = {
>> .subdir = RB_ROOT,
>> .name = "/proc",
>> };
>> -
>> -int pid_ns_prepare_proc(struct pid_namespace *ns)
>> -{
>> - struct proc_fs_context *ctx;
>> - struct fs_context *fc;
>> - struct vfsmount *mnt;
>> -
>> - fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT);
>> - if (IS_ERR(fc))
>> - return PTR_ERR(fc);
>> -
>> - if (fc->user_ns != ns->user_ns) {
>> - put_user_ns(fc->user_ns);
>> - fc->user_ns = get_user_ns(ns->user_ns);
>> - }
>> -
>> - ctx = fc->fs_private;
>> - if (ctx->pid_ns != ns) {
>> - put_pid_ns(ctx->pid_ns);
>> - get_pid_ns(ns);
>> - ctx->pid_ns = ns;
>> - }
>> -
>> - mnt = fc_mount(fc);
>> - put_fs_context(fc);
>> - if (IS_ERR(mnt))
>> - return PTR_ERR(mnt);
>> -
>> - ns->proc_mnt = mnt;
>> - return 0;
>> -}
>> -
>> -void pid_ns_release_proc(struct pid_namespace *ns)
>> -{
>> - kern_unmount(ns->proc_mnt);
>> -}
>> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
>> index 2ed6af88794b..4956e362e55e 100644
>> --- a/include/linux/pid_namespace.h
>> +++ b/include/linux/pid_namespace.h
>> @@ -33,7 +33,6 @@ struct pid_namespace {
>> unsigned int level;
>> struct pid_namespace *parent;
>> #ifdef CONFIG_PROC_FS
>> - struct vfsmount *proc_mnt;
>> struct dentry *proc_self;
>> struct dentry *proc_thread_self;
>> #endif
>> @@ -42,7 +41,6 @@ struct pid_namespace {
>> #endif
>> struct user_namespace *user_ns;
>> struct ucounts *ucounts;
>> - struct work_struct proc_work;
>> kgid_t pid_gid;
>> int hide_pid;
>> int reboot; /* group exit code if this pidns was rebooted */
>> diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
>> index 4626b1ac3b6c..e1106a077c1a 100644
>> --- a/include/linux/proc_ns.h
>> +++ b/include/linux/proc_ns.h
>> @@ -50,16 +50,11 @@ enum {
>>
>> #ifdef CONFIG_PROC_FS
>>
>> -extern int pid_ns_prepare_proc(struct pid_namespace *ns);
>> -extern void pid_ns_release_proc(struct pid_namespace *ns);
>> extern int proc_alloc_inum(unsigned int *pino);
>> extern void proc_free_inum(unsigned int inum);
>>
>> #else /* CONFIG_PROC_FS */
>>
>> -static inline int pid_ns_prepare_proc(struct pid_namespace *ns) { return 0; }
>> -static inline void pid_ns_release_proc(struct pid_namespace *ns) {}
>> -
>> static inline int proc_alloc_inum(unsigned int *inum)
>> {
>> *inum = 1;
>> diff --git a/kernel/pid.c b/kernel/pid.c
>> index ca08d6a3aa77..60820e72634c 100644
>> --- a/kernel/pid.c
>> +++ b/kernel/pid.c
>> @@ -144,9 +144,6 @@ void free_pid(struct pid *pid)
>> /* Handle a fork failure of the first process */
>> WARN_ON(ns->child_reaper);
>> ns->pid_allocated = 0;
>> - /* fall through */
>> - case 0:
>> - schedule_work(&ns->proc_work);
>> break;
>> }
>>
>> @@ -247,11 +244,6 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
>> tmp = tmp->parent;
>> }
>>
>> - if (unlikely(is_child_reaper(pid))) {
>> - if (pid_ns_prepare_proc(ns))
>> - goto out_free;
>> - }
>> -
>> get_pid_ns(ns);
>> refcount_set(&pid->count, 1);
>> for (type = 0; type < PIDTYPE_MAX; ++type)
>> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
>> index d40017e79ebe..318fcc6ba301 100644
>> --- a/kernel/pid_namespace.c
>> +++ b/kernel/pid_namespace.c
>> @@ -57,12 +57,6 @@ static struct kmem_cache *create_pid_cachep(unsigned int level)
>> return READ_ONCE(*pkc);
>> }
>>
>> -static void proc_cleanup_work(struct work_struct *work)
>
> There's a comment in kernel/pid_namespace.c that references
> proc_cleanup_work(). Can you please remove that as well?
Good catch. It isn't immediately obvious to me how that sentence
needs to be updated but it should be done.
Eric
>> -{
>> - struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
>> - pid_ns_release_proc(ns);
>> -}
>> -
>> static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
>> {
>> return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
>> @@ -114,7 +108,6 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
>> ns->user_ns = get_user_ns(user_ns);
>> ns->ucounts = ucounts;
>> ns->pid_allocated = PIDNS_ADDING;
>> - INIT_WORK(&ns->proc_work, proc_cleanup_work);
>>
>> return ns;
>>
>> --
>> 2.25.0
>>
next prev parent reply other threads:[~2020-02-28 21:42 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 15:05 [PATCH v8 00/11] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 01/11] proc: Rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 02/11] proc: add proc_fs_info struct to store proc information Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 03/11] proc: move /proc/{self|thread-self} dentries to proc_fs_info Alexey Gladkov
2020-02-10 18:23 ` Andy Lutomirski
2020-02-12 15:00 ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 04/11] proc: move hide_pid, pid_gid from pid_namespace " Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 05/11] proc: add helpers to set and get proc hidepid and gid mount options Alexey Gladkov
2020-02-10 18:30 ` Andy Lutomirski
2020-02-12 14:57 ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 06/11] proc: support mounting procfs instances inside same pid namespace Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Alexey Gladkov
2020-02-10 17:46 ` Linus Torvalds
2020-02-10 19:23 ` Al Viro
2020-02-11 1:36 ` Eric W. Biederman
2020-02-11 4:01 ` Eric W. Biederman
2020-02-12 14:49 ` Alexey Gladkov
2020-02-12 14:59 ` Eric W. Biederman
2020-02-12 17:08 ` Alexey Gladkov
2020-02-12 18:45 ` Linus Torvalds
2020-02-12 19:16 ` Eric W. Biederman
2020-02-12 19:49 ` Linus Torvalds
2020-02-12 20:03 ` Al Viro
2020-02-12 20:35 ` Linus Torvalds
2020-02-12 20:38 ` Al Viro
2020-02-12 20:41 ` Al Viro
2020-02-12 21:02 ` Linus Torvalds
2020-02-12 21:46 ` Eric W. Biederman
2020-02-13 0:48 ` Linus Torvalds
2020-02-13 4:37 ` Eric W. Biederman
2020-02-13 5:55 ` Al Viro
2020-02-13 21:30 ` Linus Torvalds
2020-02-13 22:23 ` Al Viro
2020-02-13 22:47 ` Linus Torvalds
2020-02-14 14:15 ` Eric W. Biederman
2020-02-14 3:48 ` Eric W. Biederman
2020-02-20 20:46 ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Eric W. Biederman
2020-02-20 20:47 ` [PATCH 1/7] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-20 20:48 ` [PATCH 2/7] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 20:49 ` [PATCH 3/7] proc: Mov rcu_read_(lock|unlock) in proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 22:33 ` Linus Torvalds
2020-02-20 20:49 ` [PATCH 4/7] proc: Use d_invalidate " Eric W. Biederman
2020-02-20 22:43 ` Linus Torvalds
2020-02-20 22:54 ` Al Viro
2020-02-20 23:00 ` Linus Torvalds
2020-02-20 23:03 ` Al Viro
2020-02-20 23:39 ` Eric W. Biederman
2020-02-20 20:51 ` [PATCH 5/7] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-20 20:52 ` [PATCH 6/7] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-20 20:52 ` [PATCH 7/7] proc: Ensure we see the exit of each process tid exactly once Eric W. Biederman
2020-02-21 16:50 ` Oleg Nesterov
2020-02-22 15:46 ` Eric W. Biederman
2020-02-20 23:02 ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Linus Torvalds
2020-02-20 23:07 ` Al Viro
2020-02-20 23:37 ` Eric W. Biederman
2020-02-24 16:25 ` [PATCH v2 0/6] " Eric W. Biederman
2020-02-24 16:26 ` [PATCH v2 1/6] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-24 16:27 ` [PATCH v2 2/6] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:27 ` [PATCH v2 3/6] proc: In proc_prune_siblings_dcache cache an aquired super block Eric W. Biederman
2020-02-24 16:28 ` [PATCH v2 4/6] proc: Use d_invalidate in proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:28 ` [PATCH v2 5/6] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-24 16:29 ` [PATCH v2 6/6] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-28 20:17 ` [PATCH 0/3] proc: Actually honor the mount options Eric W. Biederman
2020-02-28 20:18 ` [PATCH 1/3] uml: Don't consult current to find the proc_mnt in mconsole_proc Eric W. Biederman
2020-02-28 20:18 ` [PATCH 2/3] uml: Create a private mount of proc for mconsole Eric W. Biederman
2020-02-28 20:30 ` Christian Brauner
2020-02-28 21:28 ` Eric W. Biederman
2020-02-28 21:59 ` Christian Brauner
2020-02-28 20:19 ` [PATCH 3/3] proc: Remove the now unnecessary internal mount of proc Eric W. Biederman
2020-02-28 20:39 ` Christian Brauner
2020-02-28 21:40 ` Eric W. Biederman [this message]
2020-02-28 22:34 ` [PATCH 4/3] pid: Improve the comment about waiting in zap_pid_ns_processes Eric W. Biederman
2020-02-29 2:59 ` Christian Brauner
2020-02-14 3:49 ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Eric W. Biederman
2020-02-12 19:47 ` Al Viro
2020-02-11 22:45 ` Al Viro
2020-02-12 14:26 ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-02-10 16:29 ` Jordan Glover
2020-02-12 14:34 ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 09/11] proc: add option to mount only a pids subset Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 10/11] docs: proc: add documentation for "hidepid=4" and "subset=pidfs" options and new mount behavior Alexey Gladkov
2020-02-10 18:29 ` Andy Lutomirski
2020-02-12 16:03 ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 11/11] proc: Move hidepid values to uapi as they are user interface to mount Alexey Gladkov
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