linux-kernel - Re: [PATCH] udmabuf: validate ubuf->pagecount

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Message-ID: <20220118065650.fi74ebzqmmz4e5io@sirius.home.kraxel.org>
Date:   Tue, 18 Jan 2022 07:56:50 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     sumit.semwal@...aro.org, christian.koenig@....com,
        daniel.vetter@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        linux-kernel@...r.kernel.org,
        syzbot+2c56b725ec547fa9cb29@...kaller.appspotmail.com
Subject: Re: [PATCH] udmabuf: validate ubuf->pagecount

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@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
> ---

Pushed to drm-misc-next.

thanks,
  Gerd