linux-kernel - [PATCH] Revert "bpf: remove unnecessary rcu_read_{lock,unlock}() in multi-uprobe attach logic"

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Message-ID: <20250520054943.5002-1-xuewen.yan@unisoc.com>
Date: Tue, 20 May 2025 13:49:43 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <song@...nel.org>, <jolsa@...nel.org>, <andrii@...nel.org>,
        <daniel@...earbox.net>, <rostedt@...dmis.org>, <ast@...nel.org>,
        <mhiramat@...nel.org>
CC: <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>, <xuewen.yan94@...il.com>,
        <di.shen@...soc.com>
Subject: [PATCH] Revert "bpf: remove unnecessary rcu_read_{lock,unlock}() in multi-uprobe attach logic"

From: Di Shen <di.shen@...soc.com>

This reverts commit 4a8f635a60540888dab3804992e86410360339c8.

Althought get_pid_task() internally already calls rcu_read_lock() and
rcu_read_unlock(), the find_vpid() was not.

The documentation for find_vpid() clearly states:

  "Must be called with the tasklist_lock or rcu_read_lock() held."

Add proper rcu_read_lock/unlock() to protect the find_vpid().

Reported-by: Xuewen Yan <xuewen.yan@...soc.com>
Signed-off-by: Di Shen <di.shen@...soc.com>
---
 kernel/trace/bpf_trace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 187dc37d61d4..0c4b6af10601 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3417,7 +3417,9 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	}
 
 	if (pid) {
+		rcu_read_lock();
 		task = get_pid_task(find_vpid(pid), PIDTYPE_TGID);
+		rcu_read_unlock();
 		if (!task) {
 			err = -ESRCH;
 			goto error_path_put;
-- 
2.25.1