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Subject[PATCH 5.3 002/135] net: separate out the msghdr copy from ___sys_{send,recv}msg()
Date
From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 4257c8ca13b084550574b8c9a667d9c90ff746eb ]

This is in preparation for enabling the io_uring helpers for sendmsg
and recvmsg to first copy the header for validation before continuing
with the operation.

There should be no functional changes in this patch.

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 | 141 ++++++++++++++++++++++++++++++++++-----------------
1 file changed, 95 insertions(+), 46 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index 6a9ab7a8b1d2c..fbe08d7df7732 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2232,15 +2232,10 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
return err < 0 ? err : 0;
}

-static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
- struct msghdr *msg_sys, unsigned int flags,
- struct used_address *used_address,
- unsigned int allowed_msghdr_flags)
+static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys,
+ unsigned int flags, struct used_address *used_address,
+ unsigned int allowed_msghdr_flags)
{
- struct compat_msghdr __user *msg_compat =
- (struct compat_msghdr __user *)msg;
- struct sockaddr_storage address;
- struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
unsigned char ctl[sizeof(struct cmsghdr) + 20]
__aligned(sizeof(__kernel_size_t));
/* 20 is size of ipv6_pktinfo */
@@ -2248,19 +2243,10 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
int ctl_len;
ssize_t err;

- msg_sys->msg_name = &address;
-
- if (MSG_CMSG_COMPAT & flags)
- err = get_compat_msghdr(msg_sys, msg_compat, NULL, &iov);
- else
- err = copy_msghdr_from_user(msg_sys, msg, NULL, &iov);
- if (err < 0)
- return err;
-
err = -ENOBUFS;

if (msg_sys->msg_controllen > INT_MAX)
- goto out_freeiov;
+ goto out;
flags |= (msg_sys->msg_flags & allowed_msghdr_flags);
ctl_len = msg_sys->msg_controllen;
if ((MSG_CMSG_COMPAT & flags) && ctl_len) {
@@ -2268,7 +2254,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
cmsghdr_from_user_compat_to_kern(msg_sys, sock->sk, ctl,
sizeof(ctl));
if (err)
- goto out_freeiov;
+ goto out;
ctl_buf = msg_sys->msg_control;
ctl_len = msg_sys->msg_controllen;
} else if (ctl_len) {
@@ -2277,7 +2263,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
if (ctl_len > sizeof(ctl)) {
ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
if (ctl_buf == NULL)
- goto out_freeiov;
+ goto out;
}
err = -EFAULT;
/*
@@ -2323,7 +2309,47 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
out_freectl:
if (ctl_buf != ctl)
sock_kfree_s(sock->sk, ctl_buf, ctl_len);
-out_freeiov:
+out:
+ return err;
+}
+
+static int sendmsg_copy_msghdr(struct msghdr *msg,
+ struct user_msghdr __user *umsg, unsigned flags,
+ struct iovec **iov)
+{
+ int err;
+
+ if (flags & MSG_CMSG_COMPAT) {
+ struct compat_msghdr __user *msg_compat;
+
+ msg_compat = (struct compat_msghdr __user *) umsg;
+ err = get_compat_msghdr(msg, msg_compat, NULL, iov);
+ } else {
+ err = copy_msghdr_from_user(msg, umsg, NULL, iov);
+ }
+ if (err < 0)
+ return err;
+
+ return 0;
+}
+
+static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
+ struct msghdr *msg_sys, unsigned int flags,
+ struct used_address *used_address,
+ unsigned int allowed_msghdr_flags)
+{
+ struct sockaddr_storage address;
+ struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+ ssize_t err;
+
+ msg_sys->msg_name = &address;
+
+ err = sendmsg_copy_msghdr(msg_sys, msg, flags, &iov);
+ if (err < 0)
+ return err;
+
+ err = ____sys_sendmsg(sock, msg_sys, flags, used_address,
+ allowed_msghdr_flags);
kfree(iov);
return err;
}
@@ -2442,33 +2468,41 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
return __sys_sendmmsg(fd, mmsg, vlen, flags, true);
}

-static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
- struct msghdr *msg_sys, unsigned int flags, int nosec)
+static int recvmsg_copy_msghdr(struct msghdr *msg,
+ struct user_msghdr __user *umsg, unsigned flags,
+ struct sockaddr __user **uaddr,
+ struct iovec **iov)
{
- struct compat_msghdr __user *msg_compat =
- (struct compat_msghdr __user *)msg;
- struct iovec iovstack[UIO_FASTIOV];
- struct iovec *iov = iovstack;
- unsigned long cmsg_ptr;
- int len;
ssize_t err;

- /* kernel mode address */
- struct sockaddr_storage addr;
-
- /* user mode address pointers */
- struct sockaddr __user *uaddr;
- int __user *uaddr_len = COMPAT_NAMELEN(msg);
-
- msg_sys->msg_name = &addr;
+ if (MSG_CMSG_COMPAT & flags) {
+ struct compat_msghdr __user *msg_compat;

- if (MSG_CMSG_COMPAT & flags)
- err = get_compat_msghdr(msg_sys, msg_compat, &uaddr, &iov);
- else
- err = copy_msghdr_from_user(msg_sys, msg, &uaddr, &iov);
+ msg_compat = (struct compat_msghdr __user *) umsg;
+ err = get_compat_msghdr(msg, msg_compat, uaddr, iov);
+ } else {
+ err = copy_msghdr_from_user(msg, umsg, uaddr, iov);
+ }
if (err < 0)
return err;

+ return 0;
+}
+
+static int ____sys_recvmsg(struct socket *sock, struct msghdr *msg_sys,
+ struct user_msghdr __user *msg,
+ struct sockaddr __user *uaddr,
+ unsigned int flags, int nosec)
+{
+ struct compat_msghdr __user *msg_compat =
+ (struct compat_msghdr __user *) msg;
+ int __user *uaddr_len = COMPAT_NAMELEN(msg);
+ struct sockaddr_storage addr;
+ unsigned long cmsg_ptr;
+ int len;
+ ssize_t err;
+
+ msg_sys->msg_name = &addr;
cmsg_ptr = (unsigned long)msg_sys->msg_control;
msg_sys->msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);

@@ -2479,7 +2513,7 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
flags |= MSG_DONTWAIT;
err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys, flags);
if (err < 0)
- goto out_freeiov;
+ goto out;
len = err;

if (uaddr != NULL) {
@@ -2487,12 +2521,12 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
msg_sys->msg_namelen, uaddr,
uaddr_len);
if (err < 0)
- goto out_freeiov;
+ goto out;
}
err = __put_user((msg_sys->msg_flags & ~MSG_CMSG_COMPAT),
COMPAT_FLAGS(msg));
if (err)
- goto out_freeiov;
+ goto out;
if (MSG_CMSG_COMPAT & flags)
err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
&msg_compat->msg_controllen);
@@ -2500,10 +2534,25 @@ static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
&msg->msg_controllen);
if (err)
- goto out_freeiov;
+ goto out;
err = len;
+out:
+ return err;
+}
+
+static int ___sys_recvmsg(struct socket *sock, struct user_msghdr __user *msg,
+ struct msghdr *msg_sys, unsigned int flags, int nosec)
+{
+ struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
+ /* user mode address pointers */
+ struct sockaddr __user *uaddr;
+ ssize_t err;
+
+ err = recvmsg_copy_msghdr(msg_sys, msg, flags, &uaddr, &iov);
+ if (err < 0)
+ return err;

-out_freeiov:
+ err = ____sys_recvmsg(sock, msg_sys, msg, uaddr, flags, nosec);
kfree(iov);
return err;
}
--
2.20.1


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