From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Fri, 10 Feb 2023 01:12:01 +0100
Subject: [PATCH] libbpf: Fix alen calculation in libbpf_nla_dump_errormsg()
References: bsc#1012628
Patch-mainline: 6.2.3
Git-commit: 17bcd27a08a21397698edf143084d7c87ce17946

[ Upstream commit 17bcd27a08a21397698edf143084d7c87ce17946 ]

The code assumes that everything that comes after nlmsgerr are nlattrs.
When calculating their size, it does not account for the initial
nlmsghdr. This may lead to accessing uninitialized memory.

Fixes: bbf48c18ee0c ("libbpf: add error reporting in XDP")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230210001210.395194-8-iii@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 tools/lib/bpf/nlattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/nlattr.c b/tools/lib/bpf/nlattr.c
index 3900d052..975e265e 100644
--- a/tools/lib/bpf/nlattr.c
+++ b/tools/lib/bpf/nlattr.c
@@ -178,7 +178,7 @@ int libbpf_nla_dump_errormsg(struct nlmsghdr *nlh)
 		hlen += nlmsg_len(&err->msg);
 
 	attr = (struct nlattr *) ((void *) err + hlen);
-	alen = nlh->nlmsg_len - hlen;
+	alen = (void *)nlh + nlh->nlmsg_len - (void *)attr;
 
 	if (libbpf_nla_parse(tb, NLMSGERR_ATTR_MAX, attr, alen,
 			     extack_policy) != 0) {
-- 
2.35.3