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Subject[PATCH 5.3 003/135] net: disallow ancillary data for __sys_{send,recv}msg_file()
Date
From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit d69e07793f891524c6bbf1e75b9ae69db4450953 ]

Only io_uring uses (and added) these, and we want to disallow the
use of sendmsg/recvmsg for anything but regular data transfers.
Use the newly added prep helper to split the msghdr copy out from
the core function, to check for msg_control and msg_controllen
settings. If either is set, we return -EINVAL.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/socket.c | 43 +++++++++++++++++++++++++++++++++++++------
1 file changed, 37 insertions(+), 6 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index fbe08d7df7732..d7a106028f0e0 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2357,12 +2357,27 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
/*
* BSD sendmsg interface
*/
-long __sys_sendmsg_sock(struct socket *sock, struct user_msghdr __user *msg,
+long __sys_sendmsg_sock(struct socket *sock, struct user_msghdr __user *umsg,
unsigned int flags)
{
- struct msghdr msg_sys;
+ struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+ struct sockaddr_storage address;
+ struct msghdr msg = { .msg_name = &address };
+ ssize_t err;
+
+ err = sendmsg_copy_msghdr(&msg, umsg, flags, &iov);
+ if (err)
+ return err;
+ /* disallow ancillary data requests from this path */
+ if (msg.msg_control || msg.msg_controllen) {
+ err = -EINVAL;
+ goto out;
+ }

- return ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL, 0);
+ err = ____sys_sendmsg(sock, &msg, flags, NULL, 0);
+out:
+ kfree(iov);
+ return err;
}

long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
@@ -2561,12 +2576,28 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
* BSD recvmsg interface
*/

-long __sys_recvmsg_sock(struct socket *sock, struct user_msghdr __user *msg,
+long __sys_recvmsg_sock(struct socket *sock, struct user_msghdr __user *umsg,
unsigned int flags)
{
- struct msghdr msg_sys;
+ struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+ struct sockaddr_storage address;
+ struct msghdr msg = { .msg_name = &address };
+ struct sockaddr __user *uaddr;
+ ssize_t err;

- return ___sys_recvmsg(sock, msg, &msg_sys, flags, 0);
+ err = recvmsg_copy_msghdr(&msg, umsg, flags, &uaddr, &iov);
+ if (err)
+ return err;
+ /* disallow ancillary data requests from this path */
+ if (msg.msg_control || msg.msg_controllen) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ err = ____sys_recvmsg(sock, &msg, umsg, uaddr, flags, 0);
+out:
+ kfree(iov);
+ return err;
}

long __sys_recvmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
--
2.20.1


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