[PATCH] netfilter: nf_tables: check if payload offset is a power of 2

[Nikolay Aleksandrov <nikolay@redhat.com>]

Add a check if payload's offset is a power of 2 when selecting ops.
The fast ops were meant for well aligned offsets, also this fixes a
small bug when using unaligned offset and length of 3 which causes
only 1 byte to be loaded because the fast ops are chosen.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
I broke the line since it was >80 chars.
This patch applies to Dave's -net tree.

 net/netfilter/nft_payload.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index a2aeb31..15a3dcb 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -135,7 +135,9 @@ nft_payload_select_ops(const struct nft_ctx *ctx,
 	if (len == 0 || len > FIELD_SIZEOF(struct nft_data, data))
 		return ERR_PTR(-EINVAL);
 
-	if (len <= 4 && IS_ALIGNED(offset, len) && base != NFT_PAYLOAD_LL_HEADER)
+	if (len <= 4 && IS_ALIGNED(offset, len) &&
+	    base != NFT_PAYLOAD_LL_HEADER &&
+	    !(offset & (offset - 1)))
 		return &nft_payload_fast_ops;
 	else
 		return &nft_payload_ops;
-- 
1.8.4.2