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esp4: add length check for UDP encapsulation

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esp_output_udp_encap can produce a length that doesn't fit in the 16
bits of a UDP header's length field. In that case, we'll send a
fragmented packet whose length is larger than IP_MAX_MTU (resulting in
"Oversized IP packet" warnings on receive) and with a bogus UDP
length.

To prevent this, add a length check to esp_output_udp_encap and return
 -EMSGSIZE on failure.

This seems to be older than git history.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Sabrina Dubroca 2019-03-25 14:30:00 +01:00 committed by Steffen Klassert
parent dbb2483b2a
commit 8dfb4eba41
1 changed files with 15 additions and 5 deletions
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20
net/ipv4/esp4.c
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@ -226,7 +226,7 @@ static void esp_output_fill_trailer(u8 *tail, int tfclen, int plen, __u8 proto)
tail[plen - 1] = proto;
}
static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
static int esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
{
int encap_type;
struct udphdr *uh;
@ -234,6 +234,7 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
__be16 sport, dport;
struct xfrm_encap_tmpl *encap = x->encap;
struct ip_esp_hdr *esph = esp->esph;
unsigned int len;
spin_lock_bh(&x->lock);
sport = encap->encap_sport;
@ -241,11 +242,14 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
encap_type = encap->encap_type;
spin_unlock_bh(&x->lock);
len = skb->len + esp->tailen - skb_transport_offset(skb);
if (len + sizeof(struct iphdr) >= IP_MAX_MTU)
return -EMSGSIZE;
uh = (struct udphdr *)esph;
uh->source = sport;
uh->dest = dport;
uh->len = htons(skb->len + esp->tailen
- skb_transport_offset(skb));
uh->len = htons(len);
uh->check = 0;
switch (encap_type) {
@ -262,6 +266,8 @@ static void esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, stru
*skb_mac_header(skb) = IPPROTO_UDP;
esp->esph = esph;
return 0;
}
int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
@ -275,8 +281,12 @@ int esp_output_head(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
int tailen = esp->tailen;
/* this is non-NULL only with UDP Encapsulation */
if (x->encap)
esp_output_udp_encap(x, skb, esp);
if (x->encap) {
int err = esp_output_udp_encap(x, skb, esp);
if (err < 0)
return err;
}
if (!skb_cloned(skb)) {
if (tailen <= skb_tailroom(skb)) {