diff options
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 13 | ||||
| -rw-r--r-- | include/linux/pid.h | 1 | ||||
| -rw-r--r-- | kernel/fork.c | 98 | ||||
| -rw-r--r-- | kernel/pid.c | 19 |
4 files changed, 104 insertions, 27 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 8f430bfad487..22fb1cf7e1fc 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -663,7 +663,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, struct fanotify_info *info = fanotify_event_info(event); unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES); unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD; - struct file *f = NULL; + struct file *f = NULL, *pidfd_file = NULL; int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD; pr_debug("%s: group=%p event=%p\n", __func__, group, event); @@ -718,7 +718,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, !pid_has_task(event->pid, PIDTYPE_TGID)) { pidfd = FAN_NOPIDFD; } else { - pidfd = pidfd_create(event->pid, 0); + pidfd = pidfd_prepare(event->pid, 0, &pidfd_file); if (pidfd < 0) pidfd = FAN_EPIDFD; } @@ -751,6 +751,9 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, if (f) fd_install(fd, f); + if (pidfd_file) + fd_install(pidfd, pidfd_file); + return metadata.event_len; out_close_fd: @@ -759,8 +762,10 @@ out_close_fd: fput(f); } - if (pidfd >= 0) - close_fd(pidfd); + if (pidfd >= 0) { + put_unused_fd(pidfd); + fput(pidfd_file); + } return ret; } diff --git a/include/linux/pid.h b/include/linux/pid.h index 343abf22092e..b75de288a8c2 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -80,6 +80,7 @@ extern struct pid *pidfd_pid(const struct file *file); struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags); struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags); int pidfd_create(struct pid *pid, unsigned int flags); +int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret); static inline struct pid *get_pid(struct pid *pid) { diff --git a/kernel/fork.c b/kernel/fork.c index d6cd5849eb51..bfe73db1c26c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1961,6 +1961,91 @@ const struct file_operations pidfd_fops = { #endif }; +/** + * __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd + * @pid: the struct pid for which to create a pidfd + * @flags: flags of the new @pidfd + * @pidfd: the pidfd to return + * + * Allocate a new file that stashes @pid and reserve a new pidfd number in the + * caller's file descriptor table. The pidfd is reserved but not installed yet. + + * The helper doesn't perform checks on @pid which makes it useful for pidfds + * created via CLONE_PIDFD where @pid has no task attached when the pidfd and + * pidfd file are prepared. + * + * If this function returns successfully the caller is responsible to either + * call fd_install() passing the returned pidfd and pidfd file as arguments in + * order to install the pidfd into its file descriptor table or they must use + * put_unused_fd() and fput() on the returned pidfd and pidfd file + * respectively. + * + * This function is useful when a pidfd must already be reserved but there + * might still be points of failure afterwards and the caller wants to ensure + * that no pidfd is leaked into its file descriptor table. + * + * Return: On success, a reserved pidfd is returned from the function and a new + * pidfd file is returned in the last argument to the function. On + * error, a negative error code is returned from the function and the + * last argument remains unchanged. + */ +static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret) +{ + int pidfd; + struct file *pidfd_file; + + if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC)) + return -EINVAL; + + pidfd = get_unused_fd_flags(O_RDWR | O_CLOEXEC); + if (pidfd < 0) + return pidfd; + + pidfd_file = anon_inode_getfile("[pidfd]", &pidfd_fops, pid, + flags | O_RDWR | O_CLOEXEC); + if (IS_ERR(pidfd_file)) { + put_unused_fd(pidfd); + return PTR_ERR(pidfd_file); + } + get_pid(pid); /* held by pidfd_file now */ + *ret = pidfd_file; + return pidfd; +} + +/** + * pidfd_prepare - allocate a new pidfd_file and reserve a pidfd + * @pid: the struct pid for which to create a pidfd + * @flags: flags of the new @pidfd + * @pidfd: the pidfd to return + * + * Allocate a new file that stashes @pid and reserve a new pidfd number in the + * caller's file descriptor table. The pidfd is reserved but not installed yet. + * + * The helper verifies that @pid is used as a thread group leader. + * + * If this function returns successfully the caller is responsible to either + * call fd_install() passing the returned pidfd and pidfd file as arguments in + * order to install the pidfd into its file descriptor table or they must use + * put_unused_fd() and fput() on the returned pidfd and pidfd file + * respectively. + * + * This function is useful when a pidfd must already be reserved but there + * might still be points of failure afterwards and the caller wants to ensure + * that no pidfd is leaked into its file descriptor table. + * + * Return: On success, a reserved pidfd is returned from the function and a new + * pidfd file is returned in the last argument to the function. On + * error, a negative error code is returned from the function and the + * last argument remains unchanged. + */ +int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret) +{ + if (!pid || !pid_has_task(pid, PIDTYPE_TGID)) + return -EINVAL; + + return __pidfd_prepare(pid, flags, ret); +} + static void __delayed_free_task(struct rcu_head *rhp) { struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); @@ -2309,21 +2394,12 @@ __latent_entropy struct task_struct *copy_process( * if the fd table isn't shared). */ if (clone_flags & CLONE_PIDFD) { - retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC); + /* Note that no task has been attached to @pid yet. */ + retval = __pidfd_prepare(pid, O_RDWR | O_CLOEXEC, &pidfile); if (retval < 0) goto bad_fork_free_pid; - pidfd = retval; - pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid, - O_RDWR | O_CLOEXEC); - if (IS_ERR(pidfile)) { - put_unused_fd(pidfd); - retval = PTR_ERR(pidfile); - goto bad_fork_free_pid; - } - get_pid(pid); /* held by pidfile now */ - retval = put_user(pidfd, args->pidfd); if (retval) goto bad_fork_put_pidfd; diff --git a/kernel/pid.c b/kernel/pid.c index 3fbc5e46b721..f93954a0384d 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -594,20 +594,15 @@ struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags) */ int pidfd_create(struct pid *pid, unsigned int flags) { - int fd; - - if (!pid || !pid_has_task(pid, PIDTYPE_TGID)) - return -EINVAL; + int pidfd; + struct file *pidfd_file; - if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC)) - return -EINVAL; - - fd = anon_inode_getfd("[pidfd]", &pidfd_fops, get_pid(pid), - flags | O_RDWR | O_CLOEXEC); - if (fd < 0) - put_pid(pid); + pidfd = pidfd_prepare(pid, flags, &pidfd_file); + if (pidfd < 0) + return pidfd; - return fd; + fd_install(pidfd, pidfd_file); + return pidfd; } /** |