igmp: limit igmpv3_newpack() packet size to IP_MAX_MTU

commit c3b704d upstream.

This is a follow up of commit 915d975 ("net: deal with integer
overflows in kmalloc_reserve()") based on David Laight feedback.

Back in 2010, I failed to realize malicious users could set dev->mtu
to arbitrary values. This mtu has been since limited to 0x7fffffff but
regardless of how big dev->mtu is, it makes no sense for igmpv3_newpack()
to allocate more than IP_MAX_MTU and risk various skb fields overflows.

Fixes: 57e1ab6 ("igmp: refine skb allocations")
Link: https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: David Laight <[email protected]>
Cc: Kyle Zeng <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: edumazet

net/ipv4/igmp.c

@@ -355,8 +355,9 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, unsigned int mtu)
 	struct flowi4 fl4;
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
-	unsigned int size = mtu;
+	unsigned int size;
 
+	size = min(mtu, IP_MAX_MTU);
 	while (1) {
 		skb = alloc_skb(size + hlen + tlen,
 				GFP_ATOMIC | __GFP_NOWARN);