• PaX Team's avatar
    x86, x32: Correct invalid use of user timespec in the kernel · 2def2ef2
    PaX Team authored
    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;
    
              if (COMPAT_USE_64BIT_TIME)
                      return __sys_recvmmsg(fd, (struct mmsghdr __user *)mmsg, vlen,
                                            flags | MSG_CMSG_COMPAT,
                                            (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 ee4fa23c ("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: default avatarPaX Team <pageexec@freemail.hu>
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    Cc: <stable@vger.kernel.org> # v3.4+
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2def2ef2
compat.c 24.8 KB