[PATCH net-next v2 3/4] af_packet: convert to getsockopt_iter

[Breno Leitao <leitao@debian.org>]

Convert AF_PACKET'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()
- For PACKET_HDRLEN which reads from optval: flip data_source to
  ITER_SOURCE, copy_from_iter(), iov_iter_revert(), then restore
  ITER_DEST before the common copy_to_iter() epilogue

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/packet/af_packet.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index bb2d88205e5a..531bcee02899 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -49,6 +49,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/ethtool.h>
+#include <linux/uio.h>
 #include <linux/filter.h>
 #include <linux/types.h>
 #include <linux/mm.h>
@@ -4051,7 +4052,7 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
 }
 
 static int packet_getsockopt(struct socket *sock, int level, int optname,
-			     char __user *optval, int __user *optlen)
+			     sockopt_t *opt)
 {
 	int len;
 	int val, lv = sizeof(val);
@@ -4065,8 +4066,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 	if (level != SOL_PACKET)
 		return -ENOPROTOOPT;
 
-	if (get_user(len, optlen))
-		return -EFAULT;
+	len = opt->optlen;
 
 	if (len < 0)
 		return -EINVAL;
@@ -4115,8 +4115,11 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 			len = sizeof(int);
 		if (len < sizeof(int))
 			return -EINVAL;
-		if (copy_from_user(&val, optval, len))
+		opt->iter.data_source = ITER_SOURCE;
+		if (copy_from_iter(&val, len, &opt->iter) != len)
 			return -EFAULT;
+		iov_iter_revert(&opt->iter, len);
+		opt->iter.data_source = ITER_DEST;
 		switch (val) {
 		case TPACKET_V1:
 			val = sizeof(struct tpacket_hdr);
@@ -4171,9 +4174,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 
 	if (len > lv)
 		len = lv;
-	if (put_user(len, optlen))
-		return -EFAULT;
-	if (copy_to_user(optval, data, len))
+	opt->optlen = len;
+	if (copy_to_iter(data, len, &opt->iter) != len)
 		return -EFAULT;
 	return 0;
 }
@@ -4672,7 +4674,7 @@ static const struct proto_ops packet_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	sock_no_shutdown,
 	.setsockopt =	packet_setsockopt,
-	.getsockopt =	packet_getsockopt,
+	.getsockopt_iter =	packet_getsockopt,
 	.sendmsg =	packet_sendmsg,
 	.recvmsg =	packet_recvmsg,
 	.mmap =		packet_mmap,

-- 
2.52.0