On Mon, Jul 27, 2020 at 05:03:10PM +0200, Jason A. Donenfeld wrote:

Hi Christoph,

On Thu, Jul 23, 2020 at 08:08:54AM +0200, Christoph Hellwig wrote:

quoted

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index da933f99b5d517..42befbf12846c0 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c

@@ -1422,7 +1422,8 @@ int ip_setsockopt(struct sock *sk, int level,
 			optname != IP_IPSEC_POLICY &&
 			optname != IP_XFRM_POLICY &&
 			!ip_mroute_opt(optname))
-		err = nf_setsockopt(sk, PF_INET, optname, optval, optlen);
+		err = nf_setsockopt(sk, PF_INET, optname, USER_SOCKPTR(optval),
+				    optlen);
 #endif
 	return err;
 }

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 4697d09c98dc3e..f2a9680303d8c0 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c

@@ -1102,7 +1102,7 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
 }
 
 static int
-do_replace(struct net *net, const void __user *user, unsigned int len)
+do_replace(struct net *net, sockptr_t arg, unsigned int len)
 {
 	int ret;
 	struct ipt_replace tmp;

@@ -1110,7 +1110,7 @@ do_replace(struct net *net, const void __user *user, unsigned int len)
 	void *loc_cpu_entry;
 	struct ipt_entry *iter;
 
-	if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
+	if (copy_from_sockptr(&tmp, arg, sizeof(tmp)) != 0)
 		return -EFAULT;
 
 	/* overflow check */

@@ -1126,8 +1126,8 @@ do_replace(struct net *net, const void __user *user, unsigned int len)
 		return -ENOMEM;
 
 	loc_cpu_entry = newinfo->entries;
-	if (copy_from_user(loc_cpu_entry, user + sizeof(tmp),
-			   tmp.size) != 0) {
+	sockptr_advance(arg, sizeof(tmp));
+	if (copy_from_sockptr(loc_cpu_entry, arg, tmp.size) != 0) {
 		ret = -EFAULT;
 		goto free_newinfo;
 	}

Something along this path seems to have broken with this patch. An
invocation of `iptables -A INPUT -m length --length 1360 -j DROP` now
fails, with

nf_setsockopt->do_replace->translate_table->check_entry_size_and_hooks:
  (unsigned char *)e + e->next_offset > limit  ==>  TRUE

resulting in the whole call chain returning -EINVAL. It bisects back to
this commit. This is on net-next.

This is another use o sockptr_advance that Ido already found a problem
in.  I'm looking into this at the moment..