Re: [PATCH] tee: add overflow check in tee_ioctl_shm_register()

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Aug 22, 2022 at 11:59:17AM +0200, Greg KH wrote:
> On Mon, Aug 22, 2022 at 11:26:21AM +0200, Jens Wiklander wrote:
> > commit 573ae4f13f630d6660008f1974c0a8a29c30e18a upstream.
> > 
> > With special lengths supplied by user space, tee_shm_register() has
> > an integer overflow when calculating the number of pages covered by a
> > supplied user space memory region.
> > 
> > This may cause pin_user_pages_fast() to do a NULL pointer dereference.
> > 
> > Fix this by adding an an explicit call to access_ok() in
> > tee_ioctl_shm_register() to catch an invalid user space address early.
> > 
> > Fixes: 033ddf12bcf5 ("tee: add register user memory")
> > Cc: stable@vger.kernel.org # 5.4
> > Reported-by: Nimish Mishra <neelam.nimish@gmail.com>
> > Reported-by: Anirban Chakraborty <ch.anirban00727@gmail.com>
> > Reported-by: Debdeep Mukhopadhyay <debdeep.mukhopadhyay@gmail.com>
> > Suggested-by: Jerome Forissier <jerome.forissier@linaro.org>
> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > [JW: backport to stable-5.4 + update commit message]
> 
> Will this also work for 4.19?

Nope, it breaks the build on 4.19.y, needs a different backport there:

  CC [M]  drivers/tee/tee_core.o
drivers/tee/tee_core.c: In function ‘tee_ioctl_shm_register’:
drivers/tee/tee_core.c:178:76: error: macro "access_ok" requires 3 arguments, but only 2 given
  178 |         if (!access_ok((void __user *)(unsigned long)data.addr, data.length))
      |                                                                            ^
In file included from ./include/linux/uaccess.h:14,
                 from drivers/tee/tee_core.c:24:
./arch/x86/include/asm/uaccess.h:98: note: macro "access_ok" defined here
   98 | #define access_ok(type, addr, size)                                     \
      |
drivers/tee/tee_core.c:178:14: error: ‘access_ok’ undeclared (first use in this function)
  178 |         if (!access_ok((void __user *)(unsigned long)data.addr, data.length))
      |              ^~~~~~~~~