linux-kernel - Re: [PATCH 0/4] Fix type confusion in page_table

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Date:   Thu, 11 May 2023 07:51:58 +0900
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ruihan Li <lrh2000@....edu.cn>
Cc:     linux-mm@...ck.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 0/4] Fix type confusion in page_table_check

On Wed, May 10, 2023 at 04:55:23PM +0800, Ruihan Li wrote:
> Recently, syzbot reported [1] ("kernel BUG in page_table_check_clear").
> The root cause is that usbdev_mmap calls remap_pfn_range on kmalloc'ed
> memory, which leads to type confusion between struct page and slab in
> page_table_check. This series of patches fixes the usb side by avoiding
> mapping slab pages into userspace, and fixes the mm side by enforcing
> that all user-accessible pages are not slab pages. A more detailed
> analysis and some discussion of how to fix the problem can also be found
> in [1].
> 
>  [1] https://lore.kernel.org/lkml/20230507135844.1231056-1-lrh2000@pku.edu.cn/T/

Can you see if you can implement Christoph's proposed change instead:
	https://lore.kernel.org/r/ZFuZVDcU81WmqEvJ@infradead.org

As it might not actually be as bad as you think to require this type of
churn.

thanks,

greg k-h