[PATCH 4.19 10/22] esp: avoid unneeded kmap_atomic call

Greg Kroah-Hartman
2021-01-22T18:52:33Z

From: Willem de Bruijn <willemb@google.com>

[ Upstream commit 9bd6b629c39e3fa9e14243a6d8820492be1a5b2e ]

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: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/esp4.c | 7 +------
net/ipv6/esp6.c | 7 +------
2 files changed, 2 insertions(+), 12 deletions(-)

--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -270,7 +270,6 @@ static int esp_output_udp_encap(struct x
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;
@@ -312,14 +311,10 @@ int esp_output_head(struct xfrm_state *x
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,
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -237,7 +237,6 @@ static void esp_output_fill_trailer(u8 *
int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
u8 *tail;
- u8 *vaddr;
int nfrags;
struct page *page;
struct sk_buff *trailer;
@@ -270,14 +269,10 @@ int esp6_output_head(struct xfrm_state *
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,