linux-kernel - [PATCH 4.17 099/101] bpf: enforce correct alignment for instructions

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Message-Id: <20180720121427.420715422@linuxfoundation.org>
Date:   Fri, 20 Jul 2018 14:14:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.17 099/101] bpf: enforce correct alignment for instructions

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

commit 9262478220eac908ae6e168c3df2c453c87e2da3 upstream.

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/filter.h |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -455,7 +455,9 @@ 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 {