commit 3c5235a67acbaf8f7a86e2d0780d34cfaea696e3
author Vaibhav Rustagi <vaibhavrustagi@google.com> Mon Mar 21 17:03:11 2022 -0700
committer COS Cherry Picker <cloud-image-release@prod.google.com> Tue Mar 22 19:03:39 2022 -0700
tree 637033999243eb5c6216f12cf9391dffc4d34e63
parent 438073c9f4709183255dbb94f624942ae730ae59

esp: Fix possible buffer overflow in ESP transformation

[ Upstream commit ebe48d368e97d007bfeb76fcb065d6cfc4c96645 ]

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.

For having the patch build on v5.10, `SKB_FRAG_PAGE_ORDER` declaration
is moved from net/core/sock.c to include/net/sock.c.

BUG=b/225430954
TEST=presubmit
RELEASE_NOTE=Fixed possible buffer overflow in ESP transformation.

cos-patch: bug
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>
Change-Id: Ibba7d1063e1e78fe8cecb2d0ae1e94a586101a93
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/31062
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>

include/net/esp.h

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

include/net/sock.h

diff --git a/include/net/sock.h b/include/net/sock.h
index bb40d4d..9426af1 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2670,6 +2670,7 @@
 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)

net/ipv4/esp4.c

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index ed9857b..e2b91fc 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -448,6 +448,7 @@
 	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 @@
 			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;

net/ipv6/esp6.c

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 7f2ffc7..e106dc3 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -483,6 +483,7 @@
 	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 @@
 			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;