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@xxxxxxxxxx> > Fixes: e94591d0d90c ("proc: Convert proc_mount to use mount_ns.") > Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > --- > fs/proc/root.c | 36 ----------------------------------- What about proc_flush_task()? Or is this on top of your other series? > 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? > -{ > - 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 >