igmp: limit igmpv3_newpack() packet size to IP_MAX_MTU

This is a follow up of commit 915d975b2ffa ("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: 57e1ab6eaddc ("igmp: refine skb allocations")
Link: https://lore.kernel.org/netdev/d273628df80f45428e739274ab9ecb72@AcuMS.aculab.com/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: David Laight <David.Laight@ACULAB.COM>
Cc: Kyle Zeng <zengyhkyle@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 0c9e768..418e5fb 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -353,8 +353,9 @@ 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);