On 05/22/2017 04:38 PM, David Miller wrote:
From: "Gustavo A. R. Silva" <garsi...@embeddedor.com>
Date: Mon, 22 May 2017 09:07:46 -0500
Execution cannot reach NET_IP_ALIGN inside the following statement:
ip_align = strict ? 2 : NET_IP_ALIGN
Addresses-Coverity-ID: 1409762
Signed-off-by: Gustavo A. R. Silva <garsi...@embeddedor.com>
---
NOTE: variable ip_align could also be removed and use value 2 directly.
Incorrect.
Some platforms define NET_IP_ALIGN to zero, so the code must remain
as is.
In the check_pkt_ptr_alignment(), when !strict you would already
return earlier from that function.
So, above test in ip_align will always give 2, meaning technically
the patch is correct, although hard-coded value less clean.
Perhaps something like the below to keep intentions more clear (and
it will get resolved during compile time anyway ...):
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a098d95..3cf1d60 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2297,8 +2297,10 @@ static inline int pskb_network_may_pull(struct sk_buff
*skb, unsigned int len)
* Since this trade off varies between architectures, we allow NET_IP_ALIGN
* to be overridden.
*/
+#define NET_IP_ALIGN_DEFAULT 2
+
#ifndef NET_IP_ALIGN
-#define NET_IP_ALIGN 2
+#define NET_IP_ALIGN NET_IP_ALIGN_DEFAULT
#endif
/*
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1eddb71..61f6aaa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -812,7 +812,7 @@ static int check_pkt_ptr_alignment(const struct
bpf_reg_state *reg,
* we force this to 2 which is universally what architectures use
* when they don't set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
*/
- ip_align = strict ? 2 : NET_IP_ALIGN;
+ ip_align = NET_IP_ALIGN ? : NET_IP_ALIGN_DEFAULT;
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);
