From a4784bae98bffc817a310b5da1aece55353cd214 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 13 Apr 2021 05:41:35 -0700 Subject: [PATCH] gro: ensure frag0 meets IP header alignment After commit cd0ebef8c563 ("virtio_net: Do not pull payload in skb->head") Guenter Roeck reported one failure in his tests using sh architecture. After much debugging, we have been able to spot silent unaligned accesses in inet_gro_receive() The issue at hand is that upper networking stacks assume their header is word-aligned. Low level drivers are supposed to reserve NET_IP_ALIGN bytes before the Ethernet header to make that happen. This patch hardens skb_gro_reset_offset() to not allow frag0 fast-path if the fragment is not properly aligned. Some arches like x86, arm64 and powerpc do not care and define NET_IP_ALIGN as 0, this extra check will be a NOP for them. Note that if frag0 is not used, GRO will call pskb_may_pull() as many times as needed to pull network and transport headers. Fixes: cd0ebef8c563 ("virtio_net: Do not pull payload in skb->head") Fixes: 20fef5c8c69c ("gro: Inline skb_gro_header and cache frag0 virtual address") Signed-off-by: Eric Dumazet Reported-by: Guenter Roeck Cc: Xuan Zhuo Cc: "Michael S. Tsirkin" Cc: Jason Wang Acked-by: Michael S. Tsirkin Tested-by: Guenter Roeck Signed-off-by: David S. Miller --- net/core/dev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index af8c1ea040b93..1f79b9aa9a3f2 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5924,7 +5924,8 @@ static void skb_gro_reset_offset(struct sk_buff *skb) NAPI_GRO_CB(skb)->frag0_len = 0; if (!skb_headlen(skb) && pinfo->nr_frags && - !PageHighMem(skb_frag_page(frag0))) { + !PageHighMem(skb_frag_page(frag0)) && + (!NET_IP_ALIGN || !(skb_frag_off(frag0) & 3))) { NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0); NAPI_GRO_CB(skb)->frag0_len = min_t(unsigned int, skb_frag_size(frag0), -- 2.39.5