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esp: limit skb_page_frag_refill use to a single page

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Commit ebe48d368e ("esp: Fix possible buffer overflow in ESP
transformation") tried to fix skb_page_frag_refill usage in ESP by
capping allocsize to 32k, but that doesn't completely solve the issue,
as skb_page_frag_refill may return a single page. If that happens, we
will write out of bounds, despite the check introduced in the previous
patch.

This patch forces COW in cases where we would end up calling
skb_page_frag_refill with a size larger than a page (first in
esp_output_head with tailen, then in esp_output_tail with
skb->data_len).

Fixes: cac2661c53 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Sabrina Dubroca 2022-04-13 10:10:50 +02:00 committed by Steffen Klassert
parent 748b82c23e
commit 5bd8baab08
3 changed files with 4 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/esp.h
View File

@ -4,8 +4,6 @@
#include <linux/skbuff.h>
#define ESP_SKB_FRAG_MAXSIZE (PAGE_SIZE << SKB_FRAG_PAGE_ORDER)
struct ip_esp_hdr;
static inline struct ip_esp_hdr *ip_esp_hdr(const struct sk_buff *skb)

5
net/ipv4/esp4.c
View File

@ -446,7 +446,6 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
struct page *page;
struct sk_buff *trailer;
int tailen = esp->tailen;
unsigned int allocsz;
/* this is non-NULL only with TCP/UDP Encapsulation */
if (x->encap) {
@ -456,8 +455,8 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
return err;
}
allocsz = ALIGN(skb->data_len + tailen, L1_CACHE_BYTES);
if (allocsz > ESP_SKB_FRAG_MAXSIZE)
if (ALIGN(tailen, L1_CACHE_BYTES) > PAGE_SIZE ||
ALIGN(skb->data_len, L1_CACHE_BYTES) > PAGE_SIZE)
goto cow;
if (!skb_cloned(skb)) {

5
net/ipv6/esp6.c
View File

@ -482,7 +482,6 @@ int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
struct page *page;
struct sk_buff *trailer;
int tailen = esp->tailen;
unsigned int allocsz;
if (x->encap) {
int err = esp6_output_encap(x, skb, esp);
@ -491,8 +490,8 @@ int esp6_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
return err;
}
allocsz = ALIGN(skb->data_len + tailen, L1_CACHE_BYTES);
if (allocsz > ESP_SKB_FRAG_MAXSIZE)
if (ALIGN(tailen, L1_CACHE_BYTES) > PAGE_SIZE ||
ALIGN(skb->data_len, L1_CACHE_BYTES) > PAGE_SIZE)
goto cow;
if (!skb_cloned(skb)) {