Patch 1/2 takes care of preventing the issue fixed by commit 11789039da53
("fou: Prevent unbounded recursion in GUE error handler") also with
UDP-Lite payloads -- I just realised this might happen from a syzbot
report.
Patch 2/2 fixes the issue for both UDP and UDP-Lite on IPv6, which I also
forgot to deal with in that same commit.
Stefano Brivio (2):
fou: Prevent unbounded recursion in GUE error handler also with
UDP-Lite
fou6: Prevent unbounded recursion in GUE error handler
net/ipv4/fou.c | 3 ++-
net/ipv6/fou6.c | 8 ++++++++
2 files changed, 10 insertions(+), 1 deletion(-)
--
2.20.1
I forgot to deal with IPv6 in commit 11789039da53 ("fou: Prevent unbounded
recursion in GUE error handler").
Now syzbot reported what might be the same type of issue, caused by
gue6_err(), that is, handling exceptions for direct UDP encapsulation in
GUE (UDP-in-UDP) leads to unbounded recursion in the GUE exception
handler.
As it probably doesn't make sense to set up GUE this way, and it's
currently not even possible to configure this, skip exception handling for
UDP (or UDP-Lite) packets encapsulated in UDP (or UDP-Lite) packets with
GUE on IPv6.
Reported-by: [email protected]
Reported-by: Willem de Bruijn <[email protected]>
Reported-by: Eric Dumazet <[email protected]>
Fixes: b8a51b38e4d4 ("fou, fou6: ICMP error handlers for FoU and GUE")
Signed-off-by: Stefano Brivio <[email protected]>
---
net/ipv6/fou6.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/ipv6/fou6.c b/net/ipv6/fou6.c
index bd675c61deb1..7da7bf3b7fe3 100644
--- a/net/ipv6/fou6.c
+++ b/net/ipv6/fou6.c
@@ -131,6 +131,14 @@ static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
if (validate_gue_flags(guehdr, optlen))
return -EINVAL;
+ /* Handling exceptions for direct UDP encapsulation in GUE would lead to
+ * recursion. Besides, this kind of encapsulation can't even be
+ * configured currently. Discard this.
+ */
+ if (guehdr->proto_ctype == IPPROTO_UDP ||
+ guehdr->proto_ctype == IPPROTO_UDPLITE)
+ return -EOPNOTSUPP;
+
skb_set_transport_header(skb, -(int)sizeof(struct icmp6hdr));
ret = gue6_err_proto_handler(guehdr->proto_ctype, skb,
opt, type, code, offset, info);
--
2.20.1
In commit 11789039da53 ("fou: Prevent unbounded recursion in GUE error
handler"), I didn't take care of the case where UDP-Lite is encapsulated
into UDP or UDP-Lite with GUE. From a syzbot report about a possibly
similar issue with GUE on IPv6, I just realised the same thing might
happen with a UDP-Lite inner payload.
Also skip exception handling for inner UDP-Lite protocol.
Fixes: 11789039da53 ("fou: Prevent unbounded recursion in GUE error handler")
Signed-off-by: Stefano Brivio <[email protected]>
---
net/ipv4/fou.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 0c9f171fb085..632863541082 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -1065,7 +1065,8 @@ static int gue_err(struct sk_buff *skb, u32 info)
* recursion. Besides, this kind of encapsulation can't even be
* configured currently. Discard this.
*/
- if (guehdr->proto_ctype == IPPROTO_UDP)
+ if (guehdr->proto_ctype == IPPROTO_UDP ||
+ guehdr->proto_ctype == IPPROTO_UDPLITE)
return -EOPNOTSUPP;
skb_set_transport_header(skb, -(int)sizeof(struct icmphdr));
--
2.20.1
From: Stefano Brivio <[email protected]>
Date: Thu, 3 Jan 2019 21:43:33 +0100
> Patch 1/2 takes care of preventing the issue fixed by commit 11789039da53
> ("fou: Prevent unbounded recursion in GUE error handler") also with
> UDP-Lite payloads -- I just realised this might happen from a syzbot
> report.
>
> Patch 2/2 fixes the issue for both UDP and UDP-Lite on IPv6, which I also
> forgot to deal with in that same commit.
Series applied, thanks.