On 11.10.21 15:32, Christian Brauner wrote:
From: Christian Brauner <christian.brauner@xxxxxxxxxx>
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@xxxxxxxxxx
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Matthew Bobrowski <repnop@xxxxxxxxxx>
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Reviewed-by: Matthew Bobrowski <repnop@xxxxxxxxxx>
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
/* v2 */
- David Hildenbrand <david@xxxxxxxxxx>:
- Also document that the caller is expected to decrease the reference
count on the returned task.
---
include/linux/pid.h | 1 +
kernel/pid.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index af308e15f174..343abf22092e 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -78,6 +78,7 @@ struct file;
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);
static inline struct pid *get_pid(struct pid *pid)
diff --git a/kernel/pid.c b/kernel/pid.c
index efe87db44683..2fc0a16ec77b 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -539,6 +539,42 @@ struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
return pid;
}
+/**
+ * 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.
*
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
