diff options
| -rw-r--r-- | include/linux/pid.h | 2 | ||||
| -rw-r--r-- | include/uapi/linux/sched.h | 1 | ||||
| -rw-r--r-- | kernel/fork.c | 107 |
3 files changed, 106 insertions, 4 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h index b6f4ba16065a..3c8ef5a199ca 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -66,6 +66,8 @@ struct pid extern struct pid init_struct_pid; +extern const struct file_operations pidfd_fops; + static inline struct pid *get_pid(struct pid *pid) { if (pid) diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 22627f80063e..ed4ee170bee2 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -10,6 +10,7 @@ #define CLONE_FS 0x00000200 /* set if fs info shared between processes */ #define CLONE_FILES 0x00000400 /* set if open files shared between processes */ #define CLONE_SIGHAND 0x00000800 /* set if signal handlers and blocked signals shared */ +#define CLONE_PIDFD 0x00001000 /* set if a pidfd should be placed in parent */ #define CLONE_PTRACE 0x00002000 /* set if we want to let tracing continue on the child too */ #define CLONE_VFORK 0x00004000 /* set if the parent wants the child to wake it up on mm_release */ #define CLONE_PARENT 0x00008000 /* set if we want to have the same parent as the cloner */ diff --git a/kernel/fork.c b/kernel/fork.c index 9dcd18aa210b..e45f0acaf451 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -11,6 +11,7 @@ * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' */ +#include <linux/anon_inodes.h> #include <linux/slab.h> #include <linux/sched/autogroup.h> #include <linux/sched/mm.h> @@ -21,6 +22,7 @@ #include <linux/sched/task.h> #include <linux/sched/task_stack.h> #include <linux/sched/cputime.h> +#include <linux/seq_file.h> #include <linux/rtmutex.h> #include <linux/init.h> #include <linux/unistd.h> @@ -1662,6 +1664,58 @@ static inline void rcu_copy_process(struct task_struct *p) #endif /* #ifdef CONFIG_TASKS_RCU */ } +static int pidfd_release(struct inode *inode, struct file *file) +{ + struct pid *pid = file->private_data; + + file->private_data = NULL; + put_pid(pid); + return 0; +} + +#ifdef CONFIG_PROC_FS +static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) +{ + struct pid_namespace *ns = proc_pid_ns(file_inode(m->file)); + struct pid *pid = f->private_data; + + seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns)); + seq_putc(m, '\n'); +} +#endif + +const struct file_operations pidfd_fops = { + .release = pidfd_release, +#ifdef CONFIG_PROC_FS + .show_fdinfo = pidfd_show_fdinfo, +#endif +}; + +/** + * pidfd_create() - Create a new pid file descriptor. + * + * @pid: struct pid that the pidfd will reference + * + * This creates a new pid file descriptor with the O_CLOEXEC flag set. + * + * Note, that this function can only be called after the fd table has + * been unshared to avoid leaking the pidfd to the new process. + * + * Return: On success, a cloexec pidfd is returned. + * On error, a negative errno number will be returned. + */ +static int pidfd_create(struct pid *pid) +{ + int fd; + + fd = anon_inode_getfd("[pidfd]", &pidfd_fops, get_pid(pid), + O_RDWR | O_CLOEXEC); + if (fd < 0) + put_pid(pid); + + return fd; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -1674,13 +1728,14 @@ static __latent_entropy struct task_struct *copy_process( unsigned long clone_flags, unsigned long stack_start, unsigned long stack_size, + int __user *parent_tidptr, int __user *child_tidptr, struct pid *pid, int trace, unsigned long tls, int node) { - int retval; + int pidfd = -1, retval; struct task_struct *p; struct multiprocess_signals delayed; @@ -1730,6 +1785,31 @@ static __latent_entropy struct task_struct *copy_process( return ERR_PTR(-EINVAL); } + if (clone_flags & CLONE_PIDFD) { + int reserved; + + /* + * - CLONE_PARENT_SETTID is useless for pidfds and also + * parent_tidptr is used to return pidfds. + * - CLONE_DETACHED is blocked so that we can potentially + * reuse it later for CLONE_PIDFD. + * - CLONE_THREAD is blocked until someone really needs it. + */ + if (clone_flags & + (CLONE_DETACHED | CLONE_PARENT_SETTID | CLONE_THREAD)) + return ERR_PTR(-EINVAL); + + /* + * Verify that parent_tidptr is sane so we can potentially + * reuse it later. + */ + if (get_user(reserved, parent_tidptr)) + return ERR_PTR(-EFAULT); + + if (reserved != 0) + return ERR_PTR(-EINVAL); + } + /* * Force any signals received before this point to be delivered * before the fork happens. Collect up signals sent to multiple @@ -1936,6 +2016,22 @@ static __latent_entropy struct task_struct *copy_process( } } + /* + * This has to happen after we've potentially unshared the file + * descriptor table (so that the pidfd doesn't leak into the child + * if the fd table isn't shared). + */ + if (clone_flags & CLONE_PIDFD) { + retval = pidfd_create(pid); + if (retval < 0) + goto bad_fork_free_pid; + + pidfd = retval; + retval = put_user(pidfd, parent_tidptr); + if (retval) + goto bad_fork_put_pidfd; + } + #ifdef CONFIG_BLOCK p->plug = NULL; #endif @@ -1996,7 +2092,7 @@ static __latent_entropy struct task_struct *copy_process( */ retval = cgroup_can_fork(p); if (retval) - goto bad_fork_free_pid; + goto bad_fork_put_pidfd; /* * From this point on we must avoid any synchronous user-space @@ -2111,6 +2207,9 @@ bad_fork_cancel_cgroup: spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); cgroup_cancel_fork(p); +bad_fork_put_pidfd: + if (clone_flags & CLONE_PIDFD) + ksys_close(pidfd); bad_fork_free_pid: cgroup_threadgroup_change_end(current); if (pid != &init_struct_pid) @@ -2176,7 +2275,7 @@ static inline void init_idle_pids(struct task_struct *idle) struct task_struct *fork_idle(int cpu) { struct task_struct *task; - task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, + task = copy_process(CLONE_VM, 0, 0, NULL, NULL, &init_struct_pid, 0, 0, cpu_to_node(cpu)); if (!IS_ERR(task)) { init_idle_pids(task); @@ -2223,7 +2322,7 @@ long _do_fork(unsigned long clone_flags, trace = 0; } - p = copy_process(clone_flags, stack_start, stack_size, + p = copy_process(clone_flags, stack_start, stack_size, parent_tidptr, child_tidptr, NULL, trace, tls, NUMA_NO_NODE); add_latent_entropy(); |