1 files changed, 18 insertions, 28 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 39a3adaa4ad1..399aca51ff75 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1712,31 +1712,6 @@ const struct file_operations pidfd_fops = {
 #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;
-}
-
 static void __delayed_free_task(struct rcu_head *rhp)
 {
         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
@@ -1774,6 +1749,7 @@ static __latent_entropy struct task_struct *copy_process(
         int pidfd = -1, retval;
         struct task_struct *p;
         struct multiprocess_signals delayed;
+        struct file *pidfile = NULL;
 
         /*
          * Don't allow sharing the root directory with processes in a different
@@ -2046,11 +2022,20 @@ static __latent_entropy struct task_struct *copy_process(
          * if the fd table isn't shared).
          */
         if (clone_flags & CLONE_PIDFD) {
-                retval = pidfd_create(pid);
+                retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
                 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);
+                        goto bad_fork_free_pid;
+                }
+                get_pid(pid);   /* held by pidfile now */
+
                 retval = put_user(pidfd, parent_tidptr);
                 if (retval)
                         goto bad_fork_put_pidfd;
@@ -2168,6 +2153,9 @@ static __latent_entropy struct task_struct *copy_process(
                 goto bad_fork_cancel_cgroup;
         }
 
+        /* past the last point of failure */
+        if (pidfile)
+                fd_install(pidfd, pidfile);
 
         init_task_pid_links(p);
         if (likely(p->pid)) {
@@ -2234,8 +2222,10 @@ bad_fork_cancel_cgroup:
 bad_fork_cgroup_threadgroup_change_end:
         cgroup_threadgroup_change_end(current);
 bad_fork_put_pidfd:
-        if (clone_flags & CLONE_PIDFD)
-                ksys_close(pidfd);
+        if (clone_flags & CLONE_PIDFD) {
+                fput(pidfile);
+                put_unused_fd(pidfd);
+        }
 bad_fork_free_pid:
         if (pid != &init_struct_pid)
                 free_pid(pid);