[PATCH v4 04/10] net/socket: Break down __sys_getsockopt

[Breno Leitao <leitao@debian.org>]

Split __sys_getsockopt() into two functions by removing the core
logic into a sub-function (do_sock_getsockopt()). This will avoid
code duplication when doing the same operation in other callers, for
instance.

do_sock_getsockopt() will be called by io_uring getsockopt() command
operation in the following patch.

The same was done for the setsockopt pair.

Suggested-by: Martin KaFai Lau <martin.lau@linux.dev>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 include/linux/bpf-cgroup.h |  2 +-
 include/net/sock.h         |  2 ++
 net/core/sock.c            |  8 -----
 net/socket.c               | 62 ++++++++++++++++++++++++--------------
 4 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index cecfe8c99f28..ffaca1ab5e8d 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -378,7 +378,7 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
 ({									       \
 	int __ret = 0;							       \
 	if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT))			       \
-		get_user(__ret, optlen);				       \
+		copy_from_sockptr(&__ret, optlen, sizeof(int));		       \
 	__ret;								       \
 })
 
diff --git a/include/net/sock.h b/include/net/sock.h
index b059f9272303..c0185121efe4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1863,6 +1863,8 @@ int sock_setsockopt(struct socket *sock, int level, int op,
 		    sockptr_t optval, unsigned int optlen);
 int do_sock_setsockopt(struct socket *sock, bool compat, int level,
 		       int optname, sockptr_t optval, int optlen);
+int do_sock_getsockopt(struct socket *sock, bool compat, int level,
+		       int optname, sockptr_t optval, sockptr_t optlen);
 
 int sk_getsockopt(struct sock *sk, int level, int optname,
 		  sockptr_t optval, sockptr_t optlen);
diff --git a/net/core/sock.c b/net/core/sock.c
index 666a17cab4f5..cf15394ed664 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2009,14 +2009,6 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 	return 0;
 }
 
-int sock_getsockopt(struct socket *sock, int level, int optname,
-		    char __user *optval, int __user *optlen)
-{
-	return sk_getsockopt(sock->sk, level, optname,
-			     USER_SOCKPTR(optval),
-			     USER_SOCKPTR(optlen));
-}
-
 /*
  * Initialize an sk_lock.
  *
diff --git a/net/socket.c b/net/socket.c
index 3bf29a27653f..c79d2b2b902e 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2332,6 +2332,42 @@ SYSCALL_DEFINE5(setsockopt, int, fd, int, level, int, optname,
 INDIRECT_CALLABLE_DECLARE(bool tcp_bpf_bypass_getsockopt(int level,
 							 int optname));
 
+int do_sock_getsockopt(struct socket *sock, bool compat, int level,
+		       int optname, sockptr_t optval, sockptr_t optlen)
+{
+	int max_optlen __maybe_unused;
+	const struct proto_ops *ops;
+	int err;
+
+	err = security_socket_getsockopt(sock, level, optname);
+	if (err)
+		return err;
+
+	ops = READ_ONCE(sock->ops);
+	if (level == SOL_SOCKET) {
+		err = sk_getsockopt(sock->sk, level, optname, optval, optlen);
+	} else if (unlikely(!ops->getsockopt)) {
+		err = -EOPNOTSUPP;
+	} else {
+		if (WARN_ONCE(optval.is_kernel || optlen.is_kernel,
+			      "Invalid argument type"))
+			return -EOPNOTSUPP;
+
+		err = ops->getsockopt(sock, level, optname, optval.user,
+				      optlen.user);
+	}
+
+	if (!compat) {
+		max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);
+		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname,
+						     optval, optlen, max_optlen,
+						     err);
+	}
+
+	return err;
+}
+EXPORT_SYMBOL(do_sock_getsockopt);
+
 /*
  *	Get a socket option. Because we don't know the option lengths we have
  *	to pass a user mode parameter for the protocols to sort out.
@@ -2339,37 +2375,17 @@ INDIRECT_CALLABLE_DECLARE(bool tcp_bpf_bypass_getsockopt(int level,
 int __sys_getsockopt(int fd, int level, int optname, char __user *optval,
 		int __user *optlen)
 {
-	int max_optlen __maybe_unused;
-	const struct proto_ops *ops;
 	int err, fput_needed;
+	bool compat = in_compat_syscall();
 	struct socket *sock;
 
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (!sock)
 		return err;
 
-	err = security_socket_getsockopt(sock, level, optname);
-	if (err)
-		goto out_put;
-
-	if (!in_compat_syscall())
-		max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);
+	err = do_sock_getsockopt(sock, compat, level, optname,
+				 USER_SOCKPTR(optval), USER_SOCKPTR(optlen));
 
-	ops = READ_ONCE(sock->ops);
-	if (level == SOL_SOCKET)
-		err = sock_getsockopt(sock, level, optname, optval, optlen);
-	else if (unlikely(!ops->getsockopt))
-		err = -EOPNOTSUPP;
-	else
-		err = ops->getsockopt(sock, level, optname, optval,
-					    optlen);
-
-	if (!in_compat_syscall())
-		err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname,
-						     USER_SOCKPTR(optval),
-						     USER_SOCKPTR(optlen),
-						     max_optlen, err);
-out_put:
 	fput_light(sock->file, fput_needed);
 	return err;
 }
-- 
2.34.1