diff options
Diffstat (limited to 'fs/pidfs.c')
| -rw-r--r-- | fs/pidfs.c | 91 |
1 files changed, 87 insertions, 4 deletions
diff --git a/fs/pidfs.c b/fs/pidfs.c index 7ffdc88dfb52..618abb1fa1b8 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -2,6 +2,7 @@ #include <linux/anon_inodes.h> #include <linux/file.h> #include <linux/fs.h> +#include <linux/cgroup.h> #include <linux/magic.h> #include <linux/mount.h> #include <linux/pid.h> @@ -114,20 +115,100 @@ static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) return poll_flags; } +static long pidfd_info(struct task_struct *task, unsigned int cmd, unsigned long arg) +{ + struct pidfd_info __user *uinfo = (struct pidfd_info __user *)arg; + size_t usize = _IOC_SIZE(cmd); + struct pidfd_info kinfo = {}; + struct user_namespace *user_ns; + const struct cred *c; + __u64 mask; +#ifdef CONFIG_CGROUPS + struct cgroup *cgrp; +#endif + + if (!uinfo) + return -EINVAL; + if (usize < PIDFD_INFO_SIZE_VER0) + return -EINVAL; /* First version, no smaller struct possible */ + + if (copy_from_user(&mask, &uinfo->mask, sizeof(mask))) + return -EFAULT; + + c = get_task_cred(task); + if (!c) + return -ESRCH; + + /* Unconditionally return identifiers and credentials, the rest only on request */ + + user_ns = current_user_ns(); + kinfo.ruid = from_kuid_munged(user_ns, c->uid); + kinfo.rgid = from_kgid_munged(user_ns, c->gid); + kinfo.euid = from_kuid_munged(user_ns, c->euid); + kinfo.egid = from_kgid_munged(user_ns, c->egid); + kinfo.suid = from_kuid_munged(user_ns, c->suid); + kinfo.sgid = from_kgid_munged(user_ns, c->sgid); + kinfo.fsuid = from_kuid_munged(user_ns, c->fsuid); + kinfo.fsgid = from_kgid_munged(user_ns, c->fsgid); + kinfo.mask |= PIDFD_INFO_CREDS; + put_cred(c); + +#ifdef CONFIG_CGROUPS + rcu_read_lock(); + cgrp = task_dfl_cgroup(task); + kinfo.cgroupid = cgroup_id(cgrp); + kinfo.mask |= PIDFD_INFO_CGROUPID; + rcu_read_unlock(); +#endif + + /* + * Copy pid/tgid last, to reduce the chances the information might be + * stale. Note that it is not possible to ensure it will be valid as the + * task might return as soon as the copy_to_user finishes, but that's ok + * and userspace expects that might happen and can act accordingly, so + * this is just best-effort. What we can do however is checking that all + * the fields are set correctly, or return ESRCH to avoid providing + * incomplete information. */ + + kinfo.ppid = task_ppid_nr_ns(task, NULL); + kinfo.tgid = task_tgid_vnr(task); + kinfo.pid = task_pid_vnr(task); + kinfo.mask |= PIDFD_INFO_PID; + + if (kinfo.pid == 0 || kinfo.tgid == 0 || (kinfo.ppid == 0 && kinfo.pid != 1)) + return -ESRCH; + + /* + * If userspace and the kernel have the same struct size it can just + * be copied. If userspace provides an older struct, only the bits that + * userspace knows about will be copied. If userspace provides a new + * struct, only the bits that the kernel knows about will be copied. + */ + if (copy_to_user(uinfo, &kinfo, min(usize, sizeof(kinfo)))) + return -EFAULT; + + return 0; +} + static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct task_struct *task __free(put_task) = NULL; struct nsproxy *nsp __free(put_nsproxy) = NULL; struct pid *pid = pidfd_pid(file); struct ns_common *ns_common = NULL; - - if (arg) - return -EINVAL; + struct pid_namespace *pid_ns; task = get_pid_task(pid, PIDTYPE_PID); if (!task) return -ESRCH; + /* Extensible IOCTL that does not open namespace FDs, take a shortcut */ + if (_IOC_NR(cmd) == _IOC_NR(PIDFD_GET_INFO)) + return pidfd_info(task, cmd, arg); + + if (arg) + return -EINVAL; + scoped_guard(task_lock, task) { nsp = task->nsproxy; if (nsp) @@ -202,7 +283,9 @@ static long pidfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case PIDFD_GET_PID_NAMESPACE: if (IS_ENABLED(CONFIG_PID_NS)) { rcu_read_lock(); - ns_common = to_ns_common( get_pid_ns(task_active_pid_ns(task))); + pid_ns = task_active_pid_ns(task); + if (pid_ns) + ns_common = to_ns_common(get_pid_ns(pid_ns)); rcu_read_unlock(); } break; |