[PATCH net-next v2 4/5] kcm: convert to getsockopt_iter

[Breno Leitao <leitao@debian.org>]

Convert KCM socket's getsockopt implementation to use the new
getsockopt_iter callback with sockopt_t.

Key changes:
- Replace (char __user *optval, int __user *optlen) with sockopt_t *opt
- Use opt->optlen for buffer length (input) and returned size (output)
- Use copy_to_iter() instead of put_user()/copy_to_user()
- Add linux/uio.h for copy_to_iter()

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/kcm/kcmsock.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 3912e75079f5e..b273213cc68d1 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -24,6 +24,7 @@
 #include <linux/workqueue.h>
 #include <linux/syscalls.h>
 #include <linux/sched/signal.h>
+#include <linux/uio.h>
 
 #include <net/kcm.h>
 #include <net/netns/generic.h>
@@ -1167,7 +1168,7 @@ static int kcm_setsockopt(struct socket *sock, int level, int optname,
 }
 
 static int kcm_getsockopt(struct socket *sock, int level, int optname,
-			  char __user *optval, int __user *optlen)
+			  sockopt_t *opt)
 {
 	struct kcm_sock *kcm = kcm_sk(sock->sk);
 	int val, len;
@@ -1175,9 +1176,7 @@ static int kcm_getsockopt(struct socket *sock, int level, int optname,
 	if (level != SOL_KCM)
 		return -ENOPROTOOPT;
 
-	if (get_user(len, optlen))
-		return -EFAULT;
-
+	len = opt->optlen;
 	if (len < 0)
 		return -EINVAL;
 
@@ -1191,9 +1190,8 @@ static int kcm_getsockopt(struct socket *sock, 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;
 }
@@ -1755,7 +1753,7 @@ static const struct proto_ops kcm_dgram_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	sock_no_shutdown,
 	.setsockopt =	kcm_setsockopt,
-	.getsockopt =	kcm_getsockopt,
+	.getsockopt_iter = kcm_getsockopt,
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,
@@ -1776,7 +1774,7 @@ static const struct proto_ops kcm_seqpacket_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	sock_no_shutdown,
 	.setsockopt =	kcm_setsockopt,
-	.getsockopt =	kcm_getsockopt,
+	.getsockopt_iter = kcm_getsockopt,
 	.sendmsg =	kcm_sendmsg,
 	.recvmsg =	kcm_recvmsg,
 	.mmap =		sock_no_mmap,

-- 
2.52.0