Christian Brauner <christian.brauner@xxxxxxxxxx> 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@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? 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 >>