netdev - [PATCH] libbpf:fix use empty function pointers in ringbuf

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Date: Mon, 5 Jun 2023 11:34:49 +0800
From: Xin Liu <liuxin350@...wei.com>
To: <daniel@...earbox.net>
CC: <andrii@...nel.org>, <ast@...nel.org>, <bpf@...r.kernel.org>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <hsinweih@....edu>,
	<jakub@...udflare.com>, <john.fastabend@...il.com>, <kuba@...nel.org>,
	<linux-kernel@...r.kernel.org>, <liuxin350@...wei.com>,
	<netdev@...r.kernel.org>, <pabeni@...hat.com>,
	<syzbot+49f6cef45247ff249498@...kaller.appspotmail.com>,
	<syzkaller-bugs@...glegroups.com>, <yanan@...wei.com>,
	<wuchangye@...wei.com>, <xiesongyang@...wei.com>, <kongweibin2@...wei.com>,
	<zhangmingyi5@...wei.com>
Subject: [PATCH] libbpf:fix use empty function pointers in ringbuf_poll

From: zhangmingyi <zhangmingyi5@...wei.com>

The sample_cb of the ring_buffer__new interface can transfer NULL. However,
the system does not check whether sample_cb is NULL during 
ring_buffer__poll, null pointer is used.

Signed-off-by: zhangmingyi <zhangmingyi5@...wei.com>
---
 tools/lib/bpf/ringbuf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 02199364db13..3661338a1d2e 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -248,7 +248,7 @@ static int64_t ringbuf_process_ring(struct ring *r)
 			got_new_data = true;
 			cons_pos += roundup_len(len);
 
-			if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
+			if (r->sample_cb && ((len & BPF_RINGBUF_DISCARD_BIT) == 0)) {
 				sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
 				err = r->sample_cb(r->ctx, sample, len);
 				if (err < 0) {
-- 
2.33.0