From b2ac545efdb8ad273df23be34aa6644067ecd3b6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 13 Apr 2021 05:41:35 -0700 Subject: gro: ensure frag0 meets IP header alignment commit 38ec4944b593fd90c5ef42aaaa53e66ae5769d04 upstream. After commit 0f6925b3e8da ("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: 0f6925b3e8da ("virtio_net: Do not pull payload in skb->head") Fixes: 78a478d0efd9 ("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 Signed-off-by: Matthieu Baerts Signed-off-by: Greg Kroah-Hartman --- include/linux/skbuff.h | 9 +++++++++ net/core/dev.c | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index de3e59329b02..2f303454a323 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2784,6 +2784,15 @@ static inline void skb_propagate_pfmemalloc(struct page *page, skb->pfmemalloc = true; } +/** + * skb_frag_off() - Returns the offset of a skb fragment + * @frag: the paged fragment + */ +static inline unsigned int skb_frag_off(const skb_frag_t *frag) +{ + return frag->page_offset; +} + /** * skb_frag_page - retrieve the page referred to by a paged fragment * @frag: the paged fragment diff --git a/net/core/dev.c b/net/core/dev.c index aa419f3162b8..ea09e0809c12 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4763,7 +4763,8 @@ static void skb_gro_reset_offset(struct sk_buff *skb) if (skb_mac_header(skb) == skb_tail_pointer(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), -- cgit v1.2.3