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: 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>

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 8b07f3a4f2db2509bed581ab549c09b621c8b7ea..a3271ec3e1627fb4f6e29da0e0fb1a638fe7e789 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -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,

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 52c2f063529fbf9e33326eb6d3887f8c810b26eb..2b804fcebcc6511d32f18d99da596f9221e98551 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -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,