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 90cd02ff77ef67f7f65e2c53127c4510c23bd4a9..9c5637d41d95168052686caf7b3ff51b517e6b9b 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 70e6c87fbe3df15c5ca6adc68b685e3a2afa21a4..d747166bb291ccf95ae8ac8d6863177cda6649e3 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 5023f59a5b9688bce1a6820db16d4794f3454206..6219d97cac7a37eb8331348847942e33338cb3c0 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)) {