udp: convert udp_lib_getsockopt to sockopt_t

In preparation for converting the proto-layer getsockopt callbacks to the
sockopt_t interface, switch udp_lib_getsockopt() to take a sockopt_t.

The thin udp_getsockopt()/udpv6_getsockopt() wrappers keep their __user
signature for now: they build a user-backed sockopt_t with
sockopt_init_user(), call the helper, and write the returned length back
to optlen. The helper uses copy_to_iter() instead of copy_to_user().
No functional change.

Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260630-getsockopt_phase2-v2-2-193335f3d4d1@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

2 files changed, 45 insertions, 13 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 70f6cbd4ef73..59248a59358c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -76,6 +76,7 @@
 
 #include <linux/bpf-cgroup.h>
 #include <linux/uaccess.h>
+#include <linux/uio.h>
 #include <asm/ioctls.h>
 #include <linux/memblock.h>
 #include <linux/highmem.h>
@@ -2995,14 +2996,13 @@ static int udp_setsockopt(struct sock *sk, int level, int optname, sockptr_t opt
 }
 
 int udp_lib_getsockopt(struct sock *sk, int level, int optname,
-		       char __user *optval, int __user *optlen)
+		       sockopt_t *opt)
 {
 	struct udp_sock *up = udp_sk(sk);
 	int val, len;
 
-	if (get_user(len, optlen))
-		return -EFAULT;
-
+	len = opt->optlen;
+	/* keep the check so direct sockopt_t callers stay covered. */
 	if (len < 0)
 		return -EINVAL;
 
@@ -3037,9 +3037,8 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 		return -ENOPROTOOPT;
 	}
 
-	if (put_user(len, optlen))
-		return -EFAULT;
-	if (copy_to_user(optval, &val, len))
+	opt->optlen = len;
+	if (copy_to_iter(&val, len, &opt->iter_out) != len)
 		return -EFAULT;
 	return 0;
 }
@@ -3047,9 +3046,29 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 static int udp_getsockopt(struct sock *sk, int level, int optname,
 			  char __user *optval, int __user *optlen)
 {
-	if (level == SOL_UDP)
-		return udp_lib_getsockopt(sk, level, optname, optval, optlen);
-	return ip_getsockopt(sk, level, optname, optval, optlen);
+	sockopt_t opt;
+	int err;
+
+	/*
+	 * keep the old __user pointers, until ip_getsockopt() moves
+	 * to sockopt_t
+	 */
+	if (level != SOL_UDP)
+		return ip_getsockopt(sk, level, optname, optval, optlen);
+
+	err = sockopt_init_user(&opt, optval, optlen);
+	if (err)
+		return err;
+
+	err = udp_lib_getsockopt(sk, level, optname, &opt);
+	if (err)
+		return err;
+
+	/* optval was written by copy_to_iter() in udp_lib_getsockopt() */
+	if (put_user(opt.optlen, optlen))
+		return -EFAULT;
+
+	return 0;
 }
 
 /**
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 15e032194ecc..392e18b97045 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1826,9 +1826,22 @@ static int udpv6_setsockopt(struct sock *sk, int level, int optname,
 static int udpv6_getsockopt(struct sock *sk, int level, int optname,
 			    char __user *optval, int __user *optlen)
 {
-	if (level == SOL_UDP)
-		return udp_lib_getsockopt(sk, level, optname, optval, optlen);
-	return ipv6_getsockopt(sk, level, optname, optval, optlen);
+	sockopt_t opt;
+	int err;
+
+	if (level != SOL_UDP)
+		return ipv6_getsockopt(sk, level, optname, optval, optlen);
+
+	err = sockopt_init_user(&opt, optval, optlen);
+	if (err)
+		return err;
+
+	err = udp_lib_getsockopt(sk, level, optname, &opt);
+	if (err)
+		return err;
+	if (put_user(opt.optlen, optlen))
+		return -EFAULT;
+	return 0;
 }