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esp: Fix possible buffer overflow in ESP transformation

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The maximum message size that can be send is bigger than
the  maximum site that skb_page_frag_refill can allocate.
So it is possible to write beyond the allocated buffer.

Fix this by doing a fallback to COW in that case.

v2:

Avoid get get_order() costs as suggested by Linus Torvalds.

Fixes: cac2661c53 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a ("esp6: Avoid skb_cow_data whenever possible")
Reported-by: valis <sec@valis.email>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Steffen Klassert 2022-03-07 13:11:39 +01:00
parent a3d9001b4e
commit ebe48d368e
3 changed files with 12 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
include/net/esp.h
View file

@ -4,6 +4,8 @@
#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

@ -446,6 +446,7 @@ 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) {
@ -455,6 +456,10 @@ 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)
goto cow;
if (!skb_cloned(skb)) {
if (tailen <= skb_tailroom(skb)) {
nfrags = 1;

5
net/ipv6/esp6.c
View file

@ -482,6 +482,7 @@ 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);
@ -490,6 +491,10 @@ 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)
goto cow;
if (!skb_cloned(skb)) {
if (tailen <= skb_tailroom(skb)) {
nfrags = 1;