diff options
| -rw-r--r-- | fs/pidfs.c | 59 | ||||
| -rw-r--r-- | include/linux/pidfs.h | 3 |
2 files changed, 62 insertions, 0 deletions
diff --git a/fs/pidfs.c b/fs/pidfs.c index d64a4cbeb0da..ec5f9ad09bb8 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -896,6 +896,65 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags) return pidfd_file; } +/** + * pidfs_register_pid - register a struct pid in pidfs + * @pid: pid to pin + * + * Register a struct pid in pidfs. Needs to be paired with + * pidfs_put_pid() to not risk leaking the pidfs dentry and inode. + * + * Return: On success zero, on error a negative error code is returned. + */ +int pidfs_register_pid(struct pid *pid) +{ + struct path path __free(path_put) = {}; + int ret; + + might_sleep(); + + if (!pid) + return 0; + + ret = path_from_stashed(&pid->stashed, pidfs_mnt, get_pid(pid), &path); + if (unlikely(ret)) + return ret; + /* Keep the dentry and only put the reference to the mount. */ + path.dentry = NULL; + return 0; +} + +/** + * pidfs_get_pid - pin a struct pid through pidfs + * @pid: pid to pin + * + * Similar to pidfs_register_pid() but only valid if the caller knows + * there's a reference to the @pid through a dentry already that can't + * go away. + */ +void pidfs_get_pid(struct pid *pid) +{ + if (!pid) + return; + WARN_ON_ONCE(!stashed_dentry_get(&pid->stashed)); +} + +/** + * pidfs_put_pid - drop a pidfs reference + * @pid: pid to drop + * + * Drop a reference to @pid via pidfs. This is only safe if the + * reference has been taken via pidfs_get_pid(). + */ +void pidfs_put_pid(struct pid *pid) +{ + might_sleep(); + + if (!pid) + return; + VFS_WARN_ON_ONCE(!pid->stashed); + dput(pid->stashed); +} + static void pidfs_inode_init_once(void *data) { struct pidfs_inode *pi = data; diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 05e6f8f4a026..2676890c4d0d 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -8,5 +8,8 @@ void pidfs_add_pid(struct pid *pid); void pidfs_remove_pid(struct pid *pid); void pidfs_exit(struct task_struct *tsk); extern const struct dentry_operations pidfs_dentry_operations; +int pidfs_register_pid(struct pid *pid); +void pidfs_get_pid(struct pid *pid); +void pidfs_put_pid(struct pid *pid); #endif /* _LINUX_PID_FS_H */ |