net: Make IP alignment calulations clearer.

The assignmnet:

	ip_align = strict ? 2 : NET_IP_ALIGN;

in compare_pkt_ptr_alignment() trips up Coverity because we can only
get to this code when strict is true, therefore ip_align will always
be 2 regardless of NET_IP_ALIGN's value.

So just assign directly to '2' and explain the situation in the
comment above.

Reported-by: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1eddb713b815c3820dd996b4d34770e4c784ab71..c72cd41f5b8b9c2e05b1f65aaf4730fb9a285ed0 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -808,11 +808,15 @@ static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg,
                reg_off += reg->aux_off;
        }
 
-       /* skb->data is NET_IP_ALIGN-ed, but for strict alignment checking
-        * we force this to 2 which is universally what architectures use
-        * when they don't set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
+       /* For platforms that do not have a Kconfig enabling
+        * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
+        * NET_IP_ALIGN is universally set to '2'.  And on platforms
+        * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
+        * to this code only in strict mode where we want to emulate
+        * the NET_IP_ALIGN==2 checking.  Therefore use an
+        * unconditional IP align value of '2'.
         */
-       ip_align = strict ? 2 : NET_IP_ALIGN;
+       ip_align = 2;
        if ((ip_align + reg_off + off) % size != 0) {
                verbose("misaligned packet access off %d+%d+%d size %d\n",
                        ip_align, reg_off, off, size);