[PATCH net] bpf: enforce correct alignment for instructions

[Eric Dumazet]

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 <eduma...@google.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Martin KaFai Lau <ka...@fb.com>
Cc: Alexei Starovoitov <a...@kernel.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