[PATCH 3.12 008/133] x86, x32: Correct invalid use of user timespec in the kernel

From: Greg Kroah-Hartman
Date: Tue Feb 04 2014 - 17:31:44 EST

3.12-stable review patch. If anyone has any objections, please let me know.


From: PaX Team <pageexec@xxxxxxxxxxx>

commit 2def2ef2ae5f3990aabdbe8a755911902707d268 upstream.

The x32 case for the recvmsg() timout handling is broken:

asmlinkage long compat_sys_recvmmsg(int fd, struct compat_mmsghdr __user *mmsg,
unsigned int vlen, unsigned int flags,
struct compat_timespec __user *timeout)
int datagrams;
struct timespec ktspec;

if (flags & MSG_CMSG_COMPAT)
return -EINVAL;

return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
(struct timespec *) timeout);

The timeout pointer parameter is provided by userland (hence the __user
annotation) but for x32 syscalls it's simply cast to a kernel pointer
and is passed to __sys_recvmmsg which will eventually directly
dereference it for both reading and writing. Other callers to
__sys_recvmmsg properly copy from userland to the kernel first.

The bug was introduced by commit ee4fa23c4bfc ("compat: Use
COMPAT_USE_64BIT_TIME in net/compat.c") and should affect all kernels
since 3.4 (and perhaps vendor kernels if they backported x32 support
along with this code).

Note that CONFIG_X86_X32_ABI gets enabled at build time and only if
CONFIG_X86_X32 is enabled and ld can build x32 executables.

Other uses of COMPAT_USE_64BIT_TIME seem fine.

This addresses CVE-2014-0038.

Signed-off-by: PaX Team <pageexec@xxxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

net/compat.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

--- a/net/compat.c
+++ b/net/compat.c
@@ -780,21 +780,16 @@ asmlinkage long compat_sys_recvmmsg(int
if (flags & MSG_CMSG_COMPAT)
return -EINVAL;

- return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
- flags | MSG_CMSG_COMPAT,
- (struct timespec *) timeout);
if (timeout == NULL)
return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,

- if (get_compat_timespec(&ktspec, timeout))
+ if (compat_get_timespec(&ktspec, timeout))
return -EFAULT;

datagrams = __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
flags | MSG_CMSG_COMPAT, &ktspec);
- if (datagrams > 0 && put_compat_timespec(&ktspec, timeout))
+ if (datagrams > 0 && compat_put_timespec(&ktspec, timeout))
datagrams = -EFAULT;

return datagrams;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/