linux-kernel - [PATCH bpf-next] bpf: clear user buf when bpf_d

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Message-ID: <20250611154859.259682-1-chen.dylane@linux.dev>
Date: Wed, 11 Jun 2025 23:48:58 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: kpsingh@...nel.org,
	mattbobrowski@...gle.com,
	ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	Tao Chen <chen.dylane@...ux.dev>
Subject: [PATCH bpf-next] bpf: clear user buf when bpf_d_path failed

The bpf_d_path() function may fail. If it does,
clear the user buf, like bpf_probe_read etc.

Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
---
 kernel/trace/bpf_trace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0998cbbb963..bb1003cb271 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -916,11 +916,14 @@ BPF_CALL_3(bpf_d_path, struct path *, path, char *, buf, u32, sz)
 	 * potentially broken verifier.
 	 */
 	len = copy_from_kernel_nofault(&copy, path, sizeof(*path));
-	if (len < 0)
+	if (len < 0) {
+		memset(buf, 0, sz);
 		return len;
+	}
 
 	p = d_path(&copy, buf, sz);
 	if (IS_ERR(p)) {
+		memset(buf, 0, sz);
 		len = PTR_ERR(p);
 	} else {
 		len = buf + sz - p;
-- 
2.48.1