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gro: ensure frag0 meets IP header alignment

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commit 38ec4944b5 upstream.

After commit 0f6925b3e8 ("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: 0f6925b3e8 ("virtio_net: Do not pull payload in skb->head")
Fixes: 78a478d0ef ("gro: Inline skb_gro_header and cache frag0 virtual address")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2021-04-13 05:41:35 -07:00 committed by Greg Kroah-Hartman
parent 16851e34b6
commit d94d95ae0d
2 changed files with 11 additions and 1 deletions
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9
include/linux/skbuff.h
View file

@ -2788,6 +2788,15 @@ 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

3
net/core/dev.c
View file

@ -5400,7 +5400,8 @@ 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),