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: Vaibhav Rustagi <vaibhavrustagi@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/esp.h b/include/net/esp.h
index 117652eb6ea32a836cd269f01e70f0e3c990fbc7..465e38890ee986023fd7502d0abeb80bca3182a5 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 029df5cdeaf1254b12b68de22b97b9e9bd5a437e..f72753391accc1ef5e4fb7ebcf72e43386f0ccfb 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2438,4 +2438,7 @@ extern int sysctl_optmem_max;
 extern __u32 sysctl_wmem_default;
 extern __u32 sysctl_rmem_default;
 
+/* On 32bit arches, an skb frag is limited to 2^15 */
+#define SKB_FRAG_PAGE_ORDER    get_order(32768)
+
 #endif /* _SOCK_H */

diff --git a/net/core/sock.c b/net/core/sock.c
index 427024597204de99d390d896992d50d11f47e043..bbf9517218ff31d0092261683da0fd7d3df1db03 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2193,9 +2193,6 @@ static void sk_leave_memory_pressure(struct sock *sk)
        }
 }
 
-/* On 32bit arches, an skb frag is limited to 2^15 */
-#define SKB_FRAG_PAGE_ORDER    get_order(32768)
-
 /**
  * skb_page_frag_refill - check that a page_frag contains enough room
  * @sz: minimum size of the fragment we want to get

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 9e664b6cef132ac8c5a0cb1793953aa49b742d65..38e2aa2b2a31c8fd05c45b7b5a4bb25808c8e622 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -257,6 +257,7 @@ 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 UDP Encapsulation */
        if (x->encap) {
@@ -266,6 +267,10 @@ 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 dd1f4ed3fc2bf62e4b0456b58d326fc424a4be7c..a9baf562bb9b92a5597591c8d592108cb8e5d842 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -223,6 +223,11 @@ 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;
+
+       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)) {