[PATCH net-next 0/2] net: convert remaining CAN protocols to getsockopt_iter

[PATCH net-next 0/2] net: convert remaining CAN protocols to getsockopt_iter

[Breno Leitao]

Continue the conversion of socket protocols to the new getsockopt_iter
API by covering the two remaining CAN implementations:

  - isotp (CAN ISO-TP)
  - j1939 (SAE J1939)

With these, all CAN protocols that expose a getsockopt callback (raw,
isotp, j1939) now use .getsockopt_iter; raw was converted as part of
an earlier series.

These are mechanical, ABI-preserving conversions following the same
pattern as previously converted protocols (af_packet, can/raw,
af_netlink, af_vsock):

  - The (char __user *optval, int __user *optlen) pair is replaced with
    a single sockopt_t *opt that carries the buffer length on input and
    the returned size on output, and exposes an iov_iter for the
    copy-out path.
  - put_user()/copy_to_user() pairs are replaced with a single
    copy_to_iter() per option.
  - The wrapper in do_sock_getsockopt() handles writing optlen back to
    userspace.

No functional or ABI change is intended.

For more context about the motivation for this change, please check
commit 67fab22a7ad ("net: add getsockopt_iter callback to proto_ops")

---
Breno Leitao (2):
      can: j1939: convert to getsockopt_iter
      can: isotp: convert to getsockopt_iter

 net/can/isotp.c        | 12 +++++-------
 net/can/j1939/socket.c | 21 +++++++++++++--------
 2 files changed, 18 insertions(+), 15 deletions(-)
---
base-commit: dacf281771a9aed1a723b196120a0de8637910b9
change-id: 20260507-getsock_two_can-5d3604b1982f

Best regards,
--  
Breno Leitao <leitao@debian.org>

[PATCH net-next 1/2] can: j1939: convert to getsockopt_iter

[Breno Leitao]

Convert CAN J1939 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()
- Restructure the chained if/else if (which depended on put_user() being
  an expression) into a nested if/else block now that opt->optlen = len
  is a statement
- Add linux/uio.h for copy_to_iter()

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/can/j1939/socket.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 50a598ef5fd4a..d0c6ce607b0dc 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -17,6 +17,7 @@
 #include <linux/can/skb.h>
 #include <linux/errqueue.h>
 #include <linux/if_arp.h>
+#include <linux/uio.h>
 #include <net/can.h>
 
 #include "j1939-priv.h"
@@ -767,7 +768,7 @@ static int j1939_sk_setsockopt(struct socket *sock, int level, int optname,
 }
 
 static int j1939_sk_getsockopt(struct socket *sock, int level, int optname,
-			       char __user *optval, int __user *optlen)
+			       sockopt_t *opt)
 {
 	struct sock *sk = sock->sk;
 	struct j1939_sock *jsk = j1939_sk(sk);
@@ -779,8 +780,7 @@ static int j1939_sk_getsockopt(struct socket *sock, int level, int optname,
 
 	if (level != SOL_CAN_J1939)
 		return -EINVAL;
-	if (get_user(ulen, optlen))
-		return -EFAULT;
+	ulen = opt->optlen;
 	if (ulen < 0)
 		return -EINVAL;
 
@@ -804,11 +804,16 @@ static int j1939_sk_getsockopt(struct socket *sock, int level, int optname,
 	 * but most sockopt's are 'int' properties, and have 'len' & 'val'
 	 * left unchanged, but instead modified 'tmp'
 	 */
-	if (len > ulen)
-		ret = -EFAULT;
-	else if (put_user(len, optlen))
+	if (len > ulen) {
 		ret = -EFAULT;
-	else if (copy_to_user(optval, val, len))
+		goto no_copy;
+	}
+
+	opt->optlen = len;
+	/* Even if the copy below fails, we want to update optlen. This is
+	 * a bit confusing, but, it preserves the original behaviour
+	 */
+	if (copy_to_iter(val, len, &opt->iter_out) != len)
 		ret = -EFAULT;
 	else
 		ret = 0;
@@ -1385,7 +1390,7 @@ static const struct proto_ops j1939_ops = {
 	.listen = sock_no_listen,
 	.shutdown = sock_no_shutdown,
 	.setsockopt = j1939_sk_setsockopt,
-	.getsockopt = j1939_sk_getsockopt,
+	.getsockopt_iter = j1939_sk_getsockopt,
 	.sendmsg = j1939_sk_sendmsg,
 	.recvmsg = j1939_sk_recvmsg,
 	.mmap = sock_no_mmap,

-- 
2.52.0

[PATCH net-next 2/2] can: isotp: convert to getsockopt_iter

[Breno Leitao]

Convert CAN ISO-TP 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()

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/can/isotp.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index c48b4a818297e..1c33f09fbd338 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1500,7 +1500,7 @@ static int isotp_setsockopt(struct socket *sock, int level, int optname,
 }
 
 static int isotp_getsockopt(struct socket *sock, int level, int optname,
-			    char __user *optval, int __user *optlen)
+			    sockopt_t *opt)
 {
 	struct sock *sk = sock->sk;
 	struct isotp_sock *so = isotp_sk(sk);
@@ -1509,8 +1509,7 @@ static int isotp_getsockopt(struct socket *sock, int level, int optname,
 
 	if (level != SOL_CAN_ISOTP)
 		return -EINVAL;
-	if (get_user(len, optlen))
-		return -EFAULT;
+	len = opt->optlen;
 	if (len < 0)
 		return -EINVAL;
 
@@ -1544,9 +1543,8 @@ static int isotp_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;
 }
@@ -1718,7 +1716,7 @@ static const struct proto_ops isotp_ops = {
 	.listen = sock_no_listen,
 	.shutdown = sock_no_shutdown,
 	.setsockopt = isotp_setsockopt,
-	.getsockopt = isotp_getsockopt,
+	.getsockopt_iter = isotp_getsockopt,
 	.sendmsg = isotp_sendmsg,
 	.recvmsg = isotp_recvmsg,
 	.mmap = sock_no_mmap,

-- 
2.52.0

Re: [PATCH net-next 1/2] can: j1939: convert to getsockopt_iter

[Oleksij Rempel]

On Thu, May 07, 2026 at 02:34:47AM -0700, Breno Leitao wrote:
> Convert CAN J1939 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()
> - Restructure the chained if/else if (which depended on put_user() being
>   an expression) into a nested if/else block now that opt->optlen = len
>   is a statement
> - Add linux/uio.h for copy_to_iter()
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>

LGTM, Thank you!

Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>

Best Regards,
Oleksij
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