Commit 69879c01 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

proc: Remove the now unnecessary internal mount of proc 



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: default avatarAlistair Strachan <astrachan@google.com>
Fixes: e94591d0 ("proc: Convert proc_mount to use mount_ns.")
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 76313c70

fs/proc/root.c

+0 −36
Original line number Diff line number Diff line
@@ -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);

}

include/linux/pid_namespace.h

+0 −2
Original line number Diff line number Diff line
@@ -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 */

include/linux/proc_ns.h

+0 −5
Original line number Diff line number Diff line
@@ -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;

kernel/pid.c

+0 −8
Original line number Diff line number Diff line
@@ -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)

kernel/pid_namespace.c

+0 −7
Original line number Diff line number Diff line
@@ -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)

{

	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;

CRA Git | Maintained and supported by SUSTech CRA and CCSE