[PATCH] udmabuf: validate ubuf->pagecount

[Gerd Hoffmann]

On Thu, Dec 30, 2021 at 05:26:49PM +0300, Pavel Skripkin wrote:
> Syzbot has reported GPF in sg_alloc_append_table_from_pages(). The
> problem was in ubuf->pages == ZERO_PTR.
> 
> ubuf->pagecount is calculated from arguments passed from user-space. If
> user creates udmabuf with list.size == 0 then ubuf->pagecount will be
> also equal to zero; it causes kmalloc_array() to return ZERO_PTR.
> 
> Fix it by validating ubuf->pagecount before passing it to
> kmalloc_array().
> 
> Fixes: fbb0de795078 ("Add udmabuf misc device")
> Reported-and-tested-by: syzbot+2c56b725ec547fa9cb29 at syzkaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin at gmail.com>
> ---

Pushed to drm-misc-next.

thanks,
  Gerd