netdev - [PATCH net] bpf: enforce correct alignment for instructions

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Message-Id: <20180621002409.63136-1-edumazet@google.com>
Date:   Wed, 20 Jun 2018 17:24:09 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH net] bpf: enforce correct alignment for instructions

After commit 9facc336876f ("bpf: reject any prog that failed read-only lock")
offsetof(struct bpf_binary_header, image) became 3 instead of 4,
breaking powerpc BPF badly, since instructions need to be word aligned.

Fixes: 9facc336876f ("bpf: reject any prog that failed read-only lock")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Martin KaFai Lau <kafai@...com>
Cc: Alexei Starovoitov <ast@...nel.org>
---
 include/linux/filter.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index b615df57b7d5b2ccb468c411c3a2aae103cd2aea..20f2659dd829256d7fef206087ab3262e1e291f5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -472,7 +472,9 @@ struct sock_fprog_kern {
 struct bpf_binary_header {
 	u16 pages;
 	u16 locked:1;
-	u8 image[];
+
+	/* Some arches need word alignment for their instructions */
+	u8 image[] __aligned(4);
 };
 
 struct bpf_prog {
-- 
2.18.0.rc1.244.gcf134e6275-goog