[PATCH 5.10 29/30] esp: Fix possible buffer overflow in ESP transformation

Greg Kroah-Hartman
2022-03-21T14:12:12Z

From: Steffen Klassert <steffen.klassert@secunet.com>

commit ebe48d368e97d007bfeb76fcb065d6cfc4c96645 upstream.

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: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Reported-by: valis <sec@valis.email>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/esp.h | 2 ++
include/net/sock.h | 1 +
net/ipv4/esp4.c | 5 +++++
net/ipv6/esp6.c | 5 +++++
4 files changed, 13 insertions(+)

--- a/include/net/esp.h
+++ b/include/net/esp.h
@@ -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)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2670,6 +2670,7 @@ extern int sysctl_optmem_max;
extern __u32 sysctl_wmem_default;
extern __u32 sysctl_rmem_default;

+#define SKB_FRAG_PAGE_ORDER get_order(32768)
DECLARE_STATIC_KEY_FALSE(net_high_order_alloc_disable_key);

static inline int sk_get_wmem0(const struct sock *sk, const struct proto *proto)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -448,6 +448,7 @@ int esp_output_head(struct xfrm_state *x
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) {
@@ -457,6 +458,10 @@ int esp_output_head(struct xfrm_state *x
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;
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -483,6 +483,7 @@ int esp6_output_head(struct xfrm_state *
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);
@@ -491,6 +492,10 @@ int esp6_output_head(struct xfrm_state *
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;