netdev - [PATCH AUTOSEL 5.8 56/63] bpf: Avoid visit same object multiple times

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Date:   Mon, 24 Aug 2020 12:34:56 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yonghong Song <yhs@...com>, Alexei Starovoitov <ast@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.8 56/63] bpf: Avoid visit same object multiple times

From: Yonghong Song <yhs@...com>

[ Upstream commit e60572b8d4c39572be6857d1ec91fdf979f8775f ]

Currently when traversing all tasks, the next tid
is always increased by one. This may result in
visiting the same task multiple times in a
pid namespace.

This patch fixed the issue by seting the next
tid as pid_nr_ns(pid, ns) + 1, similar to
funciton next_tgid().

Signed-off-by: Yonghong Song <yhs@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Cc: Rik van Riel <riel@...riel.com>
Link: https://lore.kernel.org/bpf/20200818222310.2181500-1-yhs@fb.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/bpf/task_iter.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index ac7869a389990..cd7d9564bcef6 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -28,8 +28,9 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
 
 	rcu_read_lock();
 retry:
-	pid = idr_get_next(&ns->idr, tid);
+	pid = find_ge_pid(*tid, ns);
 	if (pid) {
+		*tid = pid_nr_ns(pid, ns);
 		task = get_pid_task(pid, PIDTYPE_PID);
 		if (!task) {
 			++*tid;
-- 
2.25.1