diff mbox series

[net,v2,3/3] esp: avoid unneeded kmap_atomic call

Message ID 20210109221834.3459768-4-willemdebruijn.kernel@gmail.com (mailing list archive)
State Accepted
Commit 9bd6b629c39e3fa9e14243a6d8820492be1a5b2e
Delegated to: Netdev Maintainers
Headers show
Series skb frag: kmap_atomic fixes | expand

Checks

Context Check Description
netdev/cover_letter success Link
netdev/fixes_present success Link
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net
netdev/subject_prefix success Link
netdev/cc_maintainers warning 5 maintainers not CCed: herbert@gondor.apana.org.au yoshfuji@linux-ipv6.org sowmini.varadhan@oracle.com kuznet@ms2.inr.ac.ru ilant@mellanox.com
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 44 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success Link
netdev/stable success Stable not CCed

Commit Message

Willem de Bruijn Jan. 9, 2021, 10:18 p.m. UTC 
From: Willem de Bruijn <willemb@google.com>

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>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
---
 net/ipv4/esp4.c | 7 +------
 net/ipv6/esp6.c | 7 +------
 2 files changed, 2 insertions(+), 12 deletions(-)

Comments

Steffen Klassert Jan. 11, 2021, 8:23 a.m. UTC | #1 
On Sat, Jan 09, 2021 at 05:18:34PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@google.com>
> 
> 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>
> Cc: Steffen Klassert <steffen.klassert@secunet.com>

As this patchset goes through the net tree:

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>

Thanks!
diff mbox series

Patch

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 8b07f3a4f2db..a3271ec3e162 100644
--- 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 52c2f063529f..2b804fcebcc6 100644
--- 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,