esp: Fix possible buffer overflow in ESP transformation

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>

diff --git a/include/net/esp.h b/include/net/esp.h
index 9c5637d41d95168052686caf7b3ff51b517e6b9b..90cd02ff77ef67f7f65e2c53127c4510c23bd4a9 100644 (file)
--- 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)

diff --git a/include/net/sock.h b/include/net/sock.h
index bb40d4de545caef57376884e62a73cbd8033ae48..2c11eb4abdd246ba7ae6759f79376444c6774a50 100644 (file)
--- 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)

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 4b834bbf95e074d215d32bc6354fe83e2db2dc34..9aae82145bc16d957f1ca6b98e3bbe410de3b56c 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -448,6 +448,7 @@ 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) {
@@ -457,6 +458,10 @@ 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;

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 5ce8b6c344b8a5e951ba38c78b408f669df5dbf0..20c7bef6829e1fc89188545c9f4d7f33c7937a0b 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -483,6 +483,7 @@ 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);
@@ -491,6 +492,10 @@ 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;