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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH v2 bpf-next 1/4] libbpf: add explicit padding to bpf_xdp_set_link_opts
Date: Sat, 13 Mar 2021 13:09:17 -0800	[thread overview]
Message-ID: <20210313210920.1959628-2-andrii@kernel.org> (raw)
In-Reply-To: <20210313210920.1959628-1-andrii@kernel.org>

Adding such anonymous padding fixes the issue with uninitialized portions of
bpf_xdp_set_link_opts when using LIBBPF_DECLARE_OPTS macro with inline field
initialization:

DECLARE_LIBBPF_OPTS(bpf_xdp_set_link_opts, opts, .old_fd = -1);

When such code is compiled in debug mode, compiler is generating code that
leaves padding bytes uninitialized, which triggers error inside libbpf APIs
that do strict zero initialization checks for OPTS structs.

Adding anonymous padding field fixes the issue.

Fixes: bd5ca3ef93cd ("libbpf: Add function to set link XDP fd while specifying old program")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 3c35eb401931..3d690d4e785c 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -507,6 +507,7 @@ struct xdp_link_info {
 struct bpf_xdp_set_link_opts {
 	size_t sz;
 	int old_fd;
+	size_t :0;
 };
 #define bpf_xdp_set_link_opts__last_field old_fd
 
-- 
2.24.1


  reply	other threads:[~2021-03-13 21:10 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-13 21:09 [PATCH v2 bpf-next 0/4] Build BPF selftests and its libbpf, bpftool in debug mode Andrii Nakryiko
2021-03-13 21:09 ` Andrii Nakryiko [this message]
2021-03-13 21:09 ` [PATCH v2 bpf-next 2/4] bpftool: fix maybe-uninitialized warnings Andrii Nakryiko
2021-03-13 21:09 ` [PATCH v2 bpf-next 3/4] selftests/bpf: fix maybe-uninitialized warning in xdpxceiver test Andrii Nakryiko
2021-03-13 21:09 ` [PATCH v2 bpf-next 4/4] selftests/bpf: build everything in debug mode Andrii Nakryiko
2021-03-16  5:23   ` Andrii Nakryiko
2021-03-16 21:01 ` [PATCH v2 bpf-next 0/4] Build BPF selftests and its libbpf, bpftool " Alexei Starovoitov
2021-03-16 21:36   ` Andrii Nakryiko

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