[PATCH 3/4] io_uring/cmd: Introduce SOCKET_URING_OP_SETSOCKOPT

[Breno Leitao <leitao@debian.org>]

Add initial support for SOCKET_URING_OP_SETSOCKOPT. This new command is
similar to setsockopt. This initial implementation just cares about
SOL_SOCKET level for now. The next patch implements the generic case.

Function io_uring_cmd_setsockopt() is inspired by the function
__sys_setsockopt().

"optval" is currently copied to kernel space in io_uring_cmd_setsockopt(),
so, the setsockopt() protocol callbacks operate on kernel space memory
after io_uring handlers.

Important to say that userspace needs to keep the pointer's memory alive
until the operation is completed.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 include/uapi/linux/io_uring.h |  1 +
 io_uring/uring_cmd.c          | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 8152151080db..3fe82df06abf 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -736,6 +736,7 @@ enum {
 	SOCKET_URING_OP_SIOCINQ		= 0,
 	SOCKET_URING_OP_SIOCOUTQ,
 	SOCKET_URING_OP_GETSOCKOPT,
+	SOCKET_URING_OP_SETSOCKOPT,
 };
 
 #ifdef __cplusplus
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 16c857cbf3b0..d63a3b0f93a3 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -207,6 +207,39 @@ static inline int io_uring_cmd_getsockopt(struct socket *sock,
 		return optlen;
 }
 
+static inline int io_uring_cmd_setsockopt(struct socket *sock,
+					  struct io_uring_cmd *cmd)
+{
+	void __user *optval = u64_to_user_ptr(READ_ONCE(cmd->sqe->optval));
+	int optname = READ_ONCE(cmd->sqe->optname);
+	int optlen = READ_ONCE(cmd->sqe->optlen);
+	int level = READ_ONCE(cmd->sqe->level);
+	void *koptval;
+	int err;
+
+	err = security_socket_setsockopt(sock, level, optname);
+	if (err)
+		return err;
+
+	koptval = kmalloc(optlen, GFP_KERNEL);
+	if (!koptval)
+		return -ENOMEM;
+
+	err = copy_from_user(koptval, optval, optlen);
+	if (err)
+		goto fail;
+
+	err = -EOPNOTSUPP;
+	if (level == SOL_SOCKET && !sock_use_custom_sol_socket(sock)) {
+		err = sock_setsockopt(sock, level, optname,
+				      KERNEL_SOCKPTR(koptval), optlen);
+	}
+
+fail:
+	kfree(koptval);
+	return err;
+}
+
 int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
 	struct socket *sock = cmd->file->private_data;
@@ -230,6 +263,8 @@ int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags)
 		return arg;
 	case SOCKET_URING_OP_GETSOCKOPT:
 		return io_uring_cmd_getsockopt(sock, cmd);
+	case SOCKET_URING_OP_SETSOCKOPT:
+		return io_uring_cmd_setsockopt(sock, cmd);
 	default:
 		return -EOPNOTSUPP;
 	}
-- 
2.34.1