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proc: Use PIDTYPE_TGID in next_tgid 

Combine the pid_task and thes test has_group_leader_pid into a single
dereference by using pid_task(PIDTYPE_TGID).

This makes the code simpler and proof against needing to even think
about any shenanigans that de_thread might get up to.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2020-02-24 18:53:09 -06:00
parent 0fb5ce62c5
commit 3147d8aaa0
1 changed files with 2 additions and 14 deletions
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16
fs/proc/base.c
View File

@ -3359,20 +3359,8 @@ retry:
pid = find_ge_pid(iter.tgid, ns);
if (pid) {
iter.tgid = pid_nr_ns(pid, ns);
iter.task = pid_task(pid, PIDTYPE_PID);
/* What we to know is if the pid we have find is the
* pid of a thread_group_leader. Testing for task
* being a thread_group_leader is the obvious thing
* todo but there is a window when it fails, due to
* the pid transfer logic in de_thread.
*
* So we perform the straight forward test of seeing
* if the pid we have found is the pid of a thread
* group leader, and don't worry if the task we have
* found doesn't happen to be a thread group leader.
* As we don't care in the case of readdir.
*/
if (!iter.task || !has_group_leader_pid(iter.task)) {
iter.task = pid_task(pid, PIDTYPE_TGID);
if (!iter.task) {
iter.tgid += 1;
goto retry;
}