netfilter: complete validation of user input

In my recent commit, I missed that do_replace() handlers
use copy_from_sockptr() (which I fixed), followed
by unsafe copy_from_sockptr_offset() calls.

In all functions, we can perform the @optlen validation
before even calling xt_alloc_table_info() with the following
check:

if ((u64)optlen < (u64)tmp.size + sizeof(tmp))
        return -EINVAL;

Fixes: 0c83842 ("netfilter: validate user input for expected length")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
Link: https://lore.kernel.org/r/20240409120741.3538135-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

net/ipv4/netfilter/arp_tables.c

@@ -966,6 +966,8 @@ static int do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;
 
@@ -1266,6 +1268,8 @@ static int compat_do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;
 

net/ipv4/netfilter/ip_tables.c

@@ -1118,6 +1118,8 @@ do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;
 
@@ -1504,6 +1506,8 @@ compat_do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;
 

net/ipv6/netfilter/ip6_tables.c

@@ -1135,6 +1135,8 @@ do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;
 
@@ -1513,6 +1515,8 @@ compat_do_replace(struct net *net, sockptr_t arg, unsigned int len)
 		return -ENOMEM;
 	if (tmp.num_counters == 0)
 		return -EINVAL;
+	if ((u64)len < (u64)tmp.size + sizeof(tmp))
+		return -EINVAL;
 
 	tmp.name[sizeof(tmp.name)-1] = 0;