[PATCH net-next v3 4/4] can: raw: convert to getsockopt_iter

[Breno Leitao <leitao@debian.org>]

Convert CAN raw 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 copy_to_user()
- For CAN_RAW_FILTER and CAN_RAW_XL_VCID_OPTS: on -ERANGE, set
  opt->optlen to the required buffer size. The wrapper writes this
  back to userspace even on error, preserving the existing API that
  lets userspace discover the needed allocation size.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/can/raw.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c
index eee244ffc31ec..6f9ef867a13f2 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -760,7 +760,7 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 }
 
 static int raw_getsockopt(struct socket *sock, int level, int optname,
-			  char __user *optval, int __user *optlen)
+			  sockopt_t *opt)
 {
 	struct sock *sk = sock->sk;
 	struct raw_sock *ro = raw_sk(sk);
@@ -770,8 +770,7 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 
 	if (level != SOL_CAN_RAW)
 		return -EINVAL;
-	if (get_user(len, optlen))
-		return -EFAULT;
+	len = opt->optlen;
 	if (len < 0)
 		return -EINVAL;
 
@@ -787,12 +786,12 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 			if (len < fsize) {
 				/* return -ERANGE and needed space in optlen */
 				err = -ERANGE;
-				if (put_user(fsize, optlen))
-					err = -EFAULT;
+				opt->optlen = fsize;
 			} else {
 				if (len > fsize)
 					len = fsize;
-				if (copy_to_user(optval, ro->filter, len))
+				if (copy_to_iter(ro->filter, len,
+						 &opt->iter_out) != len)
 					err = -EFAULT;
 			}
 		} else {
@@ -801,7 +800,7 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 		release_sock(sk);
 
 		if (!err)
-			err = put_user(len, optlen);
+			opt->optlen = len;
 		return err;
 	}
 	case CAN_RAW_ERR_FILTER:
@@ -845,16 +844,16 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 		if (len < sizeof(ro->raw_vcid_opts)) {
 			/* return -ERANGE and needed space in optlen */
 			err = -ERANGE;
-			if (put_user(sizeof(ro->raw_vcid_opts), optlen))
-				err = -EFAULT;
+			opt->optlen = sizeof(ro->raw_vcid_opts);
 		} else {
 			if (len > sizeof(ro->raw_vcid_opts))
 				len = sizeof(ro->raw_vcid_opts);
-			if (copy_to_user(optval, &ro->raw_vcid_opts, len))
+			if (copy_to_iter(&ro->raw_vcid_opts, len,
+					 &opt->iter_out) != len)
 				err = -EFAULT;
 		}
 		if (!err)
-			err = put_user(len, optlen);
+			opt->optlen = len;
 		return err;
 	}
 	case CAN_RAW_JOIN_FILTERS:
@@ -868,9 +867,8 @@ static int raw_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;
 }
@@ -1077,7 +1075,7 @@ static const struct proto_ops raw_ops = {
 	.listen        = sock_no_listen,
 	.shutdown      = sock_no_shutdown,
 	.setsockopt    = raw_setsockopt,
-	.getsockopt    = raw_getsockopt,
+	.getsockopt_iter = raw_getsockopt,
 	.sendmsg       = raw_sendmsg,
 	.recvmsg       = raw_recvmsg,
 	.mmap          = sock_no_mmap,

-- 
2.52.0