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esp: avoid unneeded kmap_atomic call 

esp(6)_output_head uses skb_page_frag_refill to allocate a buffer for
the esp trailer.

It accesses the page with kmap_atomic to handle highmem. But
skb_page_frag_refill can return compound pages, of which
kmap_atomic only maps the first underlying page.

skb_page_frag_refill does not return highmem, because flag
__GFP_HIGHMEM is not set. ESP uses it in the same manner as TCP.
That also does not call kmap_atomic, but directly uses page_address,
in skb_copy_to_page_nocache. Do the same for ESP.

This issue has become easier to trigger with recent kmap local
debugging feature CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP.

Fixes: cac2661c53 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
master
Willem de Bruijn 2021-01-09 17:18:34 -05:00 committed by Jakub Kicinski
parent 97550f6fa5
commit 9bd6b629c3
2 changed files with 2 additions and 12 deletions
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7
net/ipv4/esp4.c
View File

@ -443,7 +443,6 @@ static int esp_output_encap(struct xfrm_state *x, struct sk_buff *skb,
int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
u8 *tail;
u8 *vaddr;
int nfrags;
int esph_offset;
struct page *page;
@ -485,14 +484,10 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
page = pfrag->page;
get_page(page);
vaddr = kmap_atomic(page);
tail = vaddr + pfrag->offset;
tail = page_address(page) + pfrag->offset;
esp_output_fill_trailer(tail, esp->tfclen, esp->plen, esp->proto);
kunmap_atomic(vaddr);
nfrags = skb_shinfo(skb)->nr_frags;
__skb_fill_page_desc(skb, nfrags, page, pfrag->offset,

7
net/ipv6/esp6.c
View File

@ -478,7 +478,6 @@ static int esp6_output_encap(struct xfrm_state *x, struct sk_buff *skb,
int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
u8 *tail;
u8 *vaddr;
int nfrags;
int esph_offset;
struct page *page;
@ -519,14 +518,10 @@ int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
page = pfrag->page;
get_page(page);
vaddr = kmap_atomic(page);
tail = vaddr + pfrag->offset;
tail = page_address(page) + pfrag->offset;
esp_output_fill_trailer(tail, esp->tfclen, esp->plen, esp->proto);
kunmap_atomic(vaddr);
nfrags = skb_shinfo(skb)->nr_frags;
__skb_fill_page_desc(skb, nfrags, page, pfrag->offset,