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Commit fee4dfbd authored by Steffen Klassert's avatar Steffen Klassert Committed by Greg Kroah-Hartman
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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: cac2661c ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f ("esp6: Avoid skb_cow_data whenever possible")
Reported-by: default avatarvalis <sec@valis.email>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarVaibhav Rustagi <vaibhavrustagi@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2774edd4

include/net/esp.h

+2 −0
Original line number Diff line number Diff line
@@ -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

+3 −0
Original line number Diff line number Diff line
@@ -2583,6 +2583,9 @@ 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)

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/core/sock.c

+0 −2
Original line number Diff line number Diff line
@@ -2355,8 +2355,6 @@ 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)

DEFINE_STATIC_KEY_FALSE(net_high_order_alloc_disable_key);



/**

net/ipv4/esp4.c

+5 −0
Original line number Diff line number Diff line
@@ -277,6 +277,7 @@ 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) {
@@ -286,6 +287,10 @@ 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;

net/ipv6/esp6.c

+5 −0
Original line number Diff line number Diff line
@@ -230,6 +230,11 @@ 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)) {