* [PATCH net] ipv4: icmp: reject broadcast/multicast routes
@ 2026-05-19 20:08 Eric Dumazet
2026-05-19 22:30 ` David Ahern
0 siblings, 1 reply; 2+ messages in thread
From: Eric Dumazet @ 2026-05-19 20:08 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, Ido Schimmel, David Ahern, netdev, eric.dumazet,
Eric Dumazet, syzbot+c13a57c2639c2c0d03a6
syzbot was able to trigger ip_rt_bug() in a loop, using an IPv4 packet
with a crafted IPOPT_SSRR option:
options: ipv4_options {
options: array[ipv4_option] {
union ipv4_option {
ssrr: ipv4_option_route[IPOPT_SSRR] {
type: const = 0x89 (1 bytes)
length: len = 0x7 (1 bytes)
pointer: int8 = 0xa2 (1 bytes)
data: array[ipv4_addr] {
union ipv4_addr {
broadcast: const = 0xffffffff (4 bytes)
}
}
}
}
Change __icmp_send() to not send ICMP to broadcast/multicast destinations.
Fixes: c378a9c019cf ("ipv4: Give backtrace in ip_rt_bug().")
Reported-by: syzbot+c13a57c2639c2c0d03a6@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a0cc169.170a0220.1f6c2d.0004.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/ipv4/icmp.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 7eeff658b467aac6a10d7890aaa807b37d6ac3b9..23e921d313b36b00d8ae5e14846527220c9db32b 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -961,6 +961,9 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
if (IS_ERR(rt))
goto out_unlock;
+ if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
+ goto ende;
+
/* peer icmp_ratelimit */
if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
goto ende;
--
2.54.0.631.ge1b05301d1-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH net] ipv4: icmp: reject broadcast/multicast routes
2026-05-19 20:08 [PATCH net] ipv4: icmp: reject broadcast/multicast routes Eric Dumazet
@ 2026-05-19 22:30 ` David Ahern
0 siblings, 0 replies; 2+ messages in thread
From: David Ahern @ 2026-05-19 22:30 UTC (permalink / raw)
To: Eric Dumazet, David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, Ido Schimmel, netdev, eric.dumazet,
syzbot+c13a57c2639c2c0d03a6
On 5/19/26 2:08 PM, Eric Dumazet wrote:
> syzbot was able to trigger ip_rt_bug() in a loop, using an IPv4 packet
> with a crafted IPOPT_SSRR option:
>
> options: ipv4_options {
> options: array[ipv4_option] {
> union ipv4_option {
> ssrr: ipv4_option_route[IPOPT_SSRR] {
> type: const = 0x89 (1 bytes)
> length: len = 0x7 (1 bytes)
> pointer: int8 = 0xa2 (1 bytes)
> data: array[ipv4_addr] {
> union ipv4_addr {
> broadcast: const = 0xffffffff (4 bytes)
> }
> }
> }
> }
>
> Change __icmp_send() to not send ICMP to broadcast/multicast destinations.
>
> Fixes: c378a9c019cf ("ipv4: Give backtrace in ip_rt_bug().")
> Reported-by: syzbot+c13a57c2639c2c0d03a6@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/netdev/6a0cc169.170a0220.1f6c2d.0004.GAE@google.com/T/#u
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
> net/ipv4/icmp.c | 3 +++
> 1 file changed, 3 insertions(+)
>
Reviewed-by: David Ahern <dsahern@kernel.org>
^ permalink raw reply [flat|nested] 2+ messages in thread
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