esp: limit skb_page_frag_refill use to a single page

[ Upstream commit 5bd8baab087dff657e05387aee802e70304cc813 ]

Commit ebe48d368e97 ("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: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/esp.h b/include/net/esp.h
index 90cd02f..9c5637d 100644 (file)
--- a/include/net/esp.h
+++ b/include/net/esp.h
@@ -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)

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 70e6c87..d747166 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -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)) {

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 5023f59..6219d97 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -483,7 +483,6 @@ 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);
@@ -492,8 +491,8 @@ 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)) {