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

[Greg KH <greg@kroah.com>]

On Mon, Aug 22, 2022 at 05:02:53PM +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 # 4.19
> 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-4.19 + update commit message]
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> ---
>  drivers/tee/tee_core.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index d42fc2ae8592..e568cb4b2ffc 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -175,6 +175,10 @@ tee_ioctl_shm_register(struct tee_context *ctx,
>  	if (data.flags)
>  		return -EINVAL;
>  
> +	if (!access_ok(VERIFY_WRITE, (void __user *)(unsigned long)data.addr,
> +		       data.length))
> +		return -EFAULT;
> +
>  	shm = tee_shm_register(ctx, data.addr, data.length,
>  			       TEE_SHM_DMA_BUF | TEE_SHM_USER_MAPPED);
>  	if (IS_ERR(shm))
> -- 
> 2.31.1
> 

Now queued up, thanks.

greg k-h