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Message-ID: <lsq.1372214158.904571556@decadent.org.uk>
Date: Wed, 26 Jun 2013 03:35:58 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, "Andy Lutomirski" <luto@...capital.net>,
"David S. Miller" <davem@...emloft.net>
Subject: [19/26] net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg
3.2.48-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski <luto@...capital.net>
[ Upstream commits 1be374a0518a288147c6a7398792583200a67261 and
a7526eb5d06b0084ef12d7b168d008fcf516caab ]
MSG_CMSG_COMPAT is (AFAIK) not intended to be part of the API --
it's a hack that steals a bit to indicate to other networking code
that a compat entry was used. So don't allow it from a non-compat
syscall.
This prevents an oops when running this code:
int main()
{
int s;
struct sockaddr_in addr;
struct msghdr *hdr;
char *highpage = mmap((void*)(TASK_SIZE_MAX - 4096), 4096,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if (highpage == MAP_FAILED)
err(1, "mmap");
s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (s == -1)
err(1, "socket");
addr.sin_family = AF_INET;
addr.sin_port = htons(1);
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (connect(s, (struct sockaddr*)&addr, sizeof(addr)) != 0)
err(1, "connect");
void *evil = highpage + 4096 - COMPAT_MSGHDR_SIZE;
printf("Evil address is %p\n", evil);
if (syscall(__NR_sendmmsg, s, evil, 1, MSG_CMSG_COMPAT) < 0)
err(1, "sendmmsg");
return 0;
}
Cc: David S. Miller <davem@...emloft.net>
Signed-off-by: Andy Lutomirski <luto@...capital.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
include/linux/socket.h | 3 +++
net/compat.c | 13 ++++++++--
net/socket.c | 67 +++++++++++++++++++++++++++++++++-----------------
3 files changed, 59 insertions(+), 24 deletions(-)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 2acd2e2..7e9f2d3 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -336,6 +336,9 @@ extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
struct timespec;
+/* The __sys_...msg variants allow MSG_CMSG_COMPAT */
+extern long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags);
+extern long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags);
extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
unsigned int flags, struct timespec *timeout);
extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
diff --git a/net/compat.c b/net/compat.c
index 6def90e..8c979cc 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -733,19 +733,25 @@ static unsigned char nas[21] = {
asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned flags)
{
- return sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+ return __sys_sendmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
}
asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg,
unsigned vlen, unsigned int flags)
{
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
return __sys_sendmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
flags | MSG_CMSG_COMPAT);
}
asmlinkage long compat_sys_recvmsg(int fd, struct compat_msghdr __user *msg, unsigned int flags)
{
- return sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+ return __sys_recvmsg(fd, (struct msghdr __user *)msg, flags | MSG_CMSG_COMPAT);
}
asmlinkage long compat_sys_recv(int fd, void __user *buf, size_t len, unsigned flags)
@@ -767,6 +773,9 @@ asmlinkage long compat_sys_recvmmsg(int fd, struct compat_mmsghdr __user *mmsg,
int datagrams;
struct timespec ktspec;
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+
if (timeout == NULL)
return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
flags | MSG_CMSG_COMPAT, NULL);
diff --git a/net/socket.c b/net/socket.c
index 68879db..cf546a3 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1876,9 +1876,9 @@ struct used_address {
unsigned int name_len;
};
-static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
- struct msghdr *msg_sys, unsigned flags,
- struct used_address *used_address)
+static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
+ struct msghdr *msg_sys, unsigned flags,
+ struct used_address *used_address)
{
struct compat_msghdr __user *msg_compat =
(struct compat_msghdr __user *)msg;
@@ -1998,22 +1998,30 @@ out:
* BSD sendmsg interface
*/
-SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned, flags)
+long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
{
int fput_needed, err;
struct msghdr msg_sys;
- struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed);
+ struct socket *sock;
+ sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (!sock)
goto out;
- err = __sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
+ err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
fput_light(sock->file, fput_needed);
out:
return err;
}
+SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
+{
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+ return __sys_sendmsg(fd, msg, flags);
+}
+
/*
* Linux sendmmsg interface
*/
@@ -2044,15 +2052,16 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
while (datagrams < vlen) {
if (MSG_CMSG_COMPAT & flags) {
- err = __sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
- &msg_sys, flags, &used_address);
+ err = ___sys_sendmsg(sock, (struct msghdr __user *)compat_entry,
+ &msg_sys, flags, &used_address);
if (err < 0)
break;
err = __put_user(err, &compat_entry->msg_len);
++compat_entry;
} else {
- err = __sys_sendmsg(sock, (struct msghdr __user *)entry,
- &msg_sys, flags, &used_address);
+ err = ___sys_sendmsg(sock,
+ (struct msghdr __user *)entry,
+ &msg_sys, flags, &used_address);
if (err < 0)
break;
err = put_user(err, &entry->msg_len);
@@ -2076,11 +2085,13 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
unsigned int, vlen, unsigned int, flags)
{
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
return __sys_sendmmsg(fd, mmsg, vlen, flags);
}
-static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
- struct msghdr *msg_sys, unsigned flags, int nosec)
+static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
+ struct msghdr *msg_sys, unsigned flags, int nosec)
{
struct compat_msghdr __user *msg_compat =
(struct compat_msghdr __user *)msg;
@@ -2177,23 +2188,31 @@ out:
* BSD recvmsg interface
*/
-SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
- unsigned int, flags)
+long __sys_recvmsg(int fd, struct msghdr __user *msg, unsigned flags)
{
int fput_needed, err;
struct msghdr msg_sys;
- struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed);
+ struct socket *sock;
+ sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (!sock)
goto out;
- err = __sys_recvmsg(sock, msg, &msg_sys, flags, 0);
+ err = ___sys_recvmsg(sock, msg, &msg_sys, flags, 0);
fput_light(sock->file, fput_needed);
out:
return err;
}
+SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
+ unsigned int, flags)
+{
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+ return __sys_recvmsg(fd, msg, flags);
+}
+
/*
* Linux recvmmsg interface
*/
@@ -2231,17 +2250,18 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
* No need to ask LSM for more than the first datagram.
*/
if (MSG_CMSG_COMPAT & flags) {
- err = __sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
- &msg_sys, flags & ~MSG_WAITFORONE,
- datagrams);
+ err = ___sys_recvmsg(sock, (struct msghdr __user *)compat_entry,
+ &msg_sys, flags & ~MSG_WAITFORONE,
+ datagrams);
if (err < 0)
break;
err = __put_user(err, &compat_entry->msg_len);
++compat_entry;
} else {
- err = __sys_recvmsg(sock, (struct msghdr __user *)entry,
- &msg_sys, flags & ~MSG_WAITFORONE,
- datagrams);
+ err = ___sys_recvmsg(sock,
+ (struct msghdr __user *)entry,
+ &msg_sys, flags & ~MSG_WAITFORONE,
+ datagrams);
if (err < 0)
break;
err = put_user(err, &entry->msg_len);
@@ -2308,6 +2328,9 @@ SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
int datagrams;
struct timespec timeout_sys;
+ if (flags & MSG_CMSG_COMPAT)
+ return -EINVAL;
+
if (!timeout)
return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL);
--
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