netdev - [PATCH bpf 2/2] bpf: avoid visit same object multiple times

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Message-ID: <20200818162409.837005-1-yhs@fb.com>
Date:   Tue, 18 Aug 2020 09:24:09 -0700
From:   Yonghong Song <yhs@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
        Rik van Riel <riel@...riel.com>
Subject: [PATCH bpf 2/2] bpf: avoid visit same object multiple times

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().

Cc: Rik van Riel <riel@...riel.com>
Signed-off-by: Yonghong Song <yhs@...com>
---
 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 885b14cab2c0..d6e1a141ea5c 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -31,8 +31,9 @@ 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;
-- 
2.24.1