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authorChristian Brauner <christian.brauner@ubuntu.com>2021-10-11 15:32:44 +0200
committerChristian Brauner <christian.brauner@ubuntu.com>2021-10-14 13:29:18 +0200
commite9bdcdbf6936dd1fbf419e00222dc9038b7812c2 (patch)
tree1eabd32a68976f36fb256ad3c4b9723412adcea8 /kernel/pid.c
parent64570fbc14f8d7cb3fe3995f20e26bc25ce4b2cc (diff)
pid: add pidfd_get_task() helper
The number of system calls making use of pidfds is constantly increasing. Some of those new system calls duplicate the code to turn a pidfd into task_struct it refers to. Give them a simple helper for this. Link: https://lore.kernel.org/r/20211004125050.1153693-2-christian.brauner@ubuntu.com Link: https://lore.kernel.org/r/20211011133245.1703103-2-brauner@kernel.org Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Matthew Bobrowski <repnop@google.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Reviewed-by: Matthew Bobrowski <repnop@google.com> Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Diffstat (limited to 'kernel/pid.c')
-rw-r--r--kernel/pid.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index efe87db44683..2fc0a16ec77b 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -540,6 +540,42 @@ struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
}
/**
+ * pidfd_get_task() - Get the task associated with a pidfd
+ *
+ * @pidfd: pidfd for which to get the task
+ * @flags: flags associated with this pidfd
+ *
+ * Return the task associated with @pidfd. The function takes a reference on
+ * the returned task. The caller is responsible for releasing that reference.
+ *
+ * Currently, the process identified by @pidfd is always a thread-group leader.
+ * This restriction currently exists for all aspects of pidfds including pidfd
+ * creation (CLONE_PIDFD cannot be used with CLONE_THREAD) and pidfd polling
+ * (only supports thread group leaders).
+ *
+ * Return: On success, the task_struct associated with the pidfd.
+ * On error, a negative errno number will be returned.
+ */
+struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags)
+{
+ unsigned int f_flags;
+ struct pid *pid;
+ struct task_struct *task;
+
+ pid = pidfd_get_pid(pidfd, &f_flags);
+ if (IS_ERR(pid))
+ return ERR_CAST(pid);
+
+ task = get_pid_task(pid, PIDTYPE_TGID);
+ put_pid(pid);
+ if (!task)
+ return ERR_PTR(-ESRCH);
+
+ *flags = f_flags;
+ return task;
+}
+
+/**
* pidfd_create() - Create a new pid file descriptor.
*
* @pid: struct pid that the pidfd will reference