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Commit e4eda884 authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatar"Gustavo A. R. Silva" <garsilva@embeddedor.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 751da2a6

kernel/bpf/verifier.c

+8 −4
Original line number Diff line number Diff line
@@ -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.

	 */

	ip_align = strict ? 2 : NET_IP_ALIGN;

	/* 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 = 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);