netdev - [PATCH bpf-next] libbpf: Use OPTS_SET() macro in bpf_xdp

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Message-ID: <20240206125922.1992815-1-toke@redhat.com>
Date: Tue,  6 Feb 2024 13:59:22 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: Toke Høiland-Jørgensen <toke@...hat.com>,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH bpf-next] libbpf: Use OPTS_SET() macro in bpf_xdp_query()

When the feature_flags and xdp_zc_max_segs fields were added to the libbpf
bpf_xdp_query_opts, the code writing them did not use the OPTS_SET() macro.
This causes libbpf to write to those fields unconditionally, which means
that programs compiled against an older version of libbpf (with a smaller
size of the bpf_xdp_query_opts struct) will have its stack corrupted by
libbpf writing out of bounds.

The patch adding the feature_flags field has an early bail out if the
feature_flags field is not part of the opts struct (via the OPTS_HAS)
macro, but the patch adding xdp_zc_max_segs does not. For consistency, this
fix just changes the assignments to both fields to use the OPTS_SET()
macro.

Fixes: 13ce2daa259a ("xsk: add new netlink attribute dedicated for ZC max frags")
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 tools/lib/bpf/netlink.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
index 090bcf6e3b3d..68a2def17175 100644
--- a/tools/lib/bpf/netlink.c
+++ b/tools/lib/bpf/netlink.c
@@ -496,8 +496,8 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
 	if (err)
 		return libbpf_err(err);
 
-	opts->feature_flags = md.flags;
-	opts->xdp_zc_max_segs = md.xdp_zc_max_segs;
+	OPTS_SET(opts, feature_flags, md.flags);
+	OPTS_SET(opts, xdp_zc_max_segs, md.xdp_zc_max_segs);
 
 skip_feature_flags:
 	return 0;
-- 
2.43.0