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authorOleg Nesterov2023-11-14 17:32:34 +0100
committerAlexei Starovoitov2023-11-19 11:43:44 -0800
commit2d1618054f25e11c44d189dbff4a60342a4cfb4b (patch)
treef801475761d64aa6bdaed25a183a7cc23efbce55 /kernel
parent16b3129e14bf2e7505512568b11c437c840a0c19 (diff)
bpf: task_group_seq_get_next: use __next_thread() rather than next_thread()
Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c is the last user and the usage is wrong. task_group_seq_get_next() can return the group leader twice if it races with mt-thread exec which changes the group->leader's pid. Change the main loop to use __next_thread(), kill "next_tid == common->pid" check. __next_thread() can't loop forever, we can also change this code to retry if next_tid == 0. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20231114163234.GA890@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/task_iter.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 26082b97894d..51ae15e2b290 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -70,15 +70,13 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm
return NULL;
retry:
- task = next_thread(task);
+ task = __next_thread(task);
+ if (!task)
+ return NULL;
next_tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns);
- if (!next_tid || next_tid == common->pid) {
- /* Run out of tasks of a process. The tasks of a
- * thread_group are linked as circular linked list.
- */
- return NULL;
- }
+ if (!next_tid)
+ goto retry;
if (skip_if_dup_files && task->files == task->group_leader->files)
goto retry;