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Subject[PATCH] net: Unbreak compat_sys_{send,recv}msg
Date
I broke them in this commit:

commit 1be374a0518a288147c6a7398792583200a67261
Author: Andy Lutomirski <luto@amacapital.net>
Date: Wed May 22 14:07:44 2013 -0700

net: Block MSG_CMSG_COMPAT in send(m)msg and recv(m)msg

This patch adds __sys_sendmsg and __sys_sendmsg as common helpers that accept
MSG_CMSG_COMPAT and blocks MSG_CMSG_COMPAT at the syscall entrypoints. It
also reverts some unnecessary checks in sys_socketcall.

Apparently I was suffering from underscore blindness the first time around.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---

I've tested this a little, but I'm not sure I have a great test case.

If the decision is that it's better to leave this for the 3.11, I can send
a squashed version. Note that the oops that this fixes is only an oops if
the other patches in the original series are applied.

(FWIW, I wasn't sure how to submit this stuff in the first place. I submitted
some kernel hardening patches for the x86 tree that converted an access_ok
oddity in the net code into an actual oops. In a bit of looking, I couldn't
find any failure mode other than a -EFAULT return without the other patches
applied. This was clear in the patch series description but not in the
change log message for the net part.)

include/linux/socket.h | 3 +++
net/compat.c | 13 +++++++--
net/socket.c | 72 +++++++++++++++++++++++---------------------------
3 files changed, 47 insertions(+), 41 deletions(-)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 2b9f74b..e897bdc 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -321,6 +321,9 @@ 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 79ae884..f0a1ba6 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -734,19 +734,25 @@ static unsigned char nas[21] = {

asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned int 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 int 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 int flags)
@@ -768,6 +774,9 @@ 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 (COMPAT_USE_64BIT_TIME)
return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
flags | MSG_CMSG_COMPAT,
diff --git a/net/socket.c b/net/socket.c
index 0e16888..e216502 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1978,7 +1978,7 @@ struct used_address {
unsigned int name_len;
};

-static int __sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
+static int ___sys_sendmsg(struct socket *sock, struct msghdr __user *msg,
struct msghdr *msg_sys, unsigned int flags,
struct used_address *used_address)
{
@@ -2093,26 +2093,30 @@ out:
* BSD sendmsg interface
*/

-SYSCALL_DEFINE3(sendmsg, int, fd, struct msghdr __user *, msg, unsigned int, flags)
+long __sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
{
int fput_needed, err;
struct msghdr msg_sys;
struct socket *sock;

- if (flags & MSG_CMSG_COMPAT)
- return -EINVAL;
-
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
*/
@@ -2143,15 +2147,16 @@ 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);
@@ -2180,7 +2185,7 @@ SYSCALL_DEFINE4(sendmmsg, int, fd, struct mmsghdr __user *, mmsg,
return __sys_sendmmsg(fd, mmsg, vlen, flags);
}

-static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
+static int ___sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
struct msghdr *msg_sys, unsigned int flags, int nosec)
{
struct compat_msghdr __user *msg_compat =
@@ -2272,27 +2277,31 @@ 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;

- if (flags & MSG_CMSG_COMPAT)
- return -EINVAL;
-
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
*/
@@ -2330,17 +2339,18 @@ 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);
@@ -2525,31 +2535,15 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
(int __user *)a[4]);
break;
case SYS_SENDMSG:
- if (a[2] & MSG_CMSG_COMPAT) {
- err = -EINVAL;
- break;
- }
err = sys_sendmsg(a0, (struct msghdr __user *)a1, a[2]);
break;
case SYS_SENDMMSG:
- if (a[3] & MSG_CMSG_COMPAT) {
- err = -EINVAL;
- break;
- }
err = sys_sendmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3]);
break;
case SYS_RECVMSG:
- if (a[2] & MSG_CMSG_COMPAT) {
- err = -EINVAL;
- break;
- }
err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
break;
case SYS_RECVMMSG:
- if (a[3] & MSG_CMSG_COMPAT) {
- err = -EINVAL;
- break;
- }
err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3],
(struct timespec __user *)a[4]);
break;
--
1.8.1.4


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