Re: [PATCH v3 1/3] mm/swapfile: unuse_pte can map random data if swap read fails

[HORIGUCHI NAOYA(堀口 直也)]

On Sun, Apr 24, 2022 at 05:11:03PM +0800, Miaohe Lin wrote:
> There is a bug in unuse_pte(): when swap page happens to be unreadable,
> page filled with random data is mapped into user address space.  In case
> of error, a special swap entry indicating swap read fails is set to the
> page table.  So the swapcache page can be freed and the user won't end up
> with a permanently mounted swap because a sector is bad.  And if the page
> is accessed later, the user process will be killed so that corrupted data
> is never consumed.  On the other hand, if the page is never accessed, the
> user won't even notice it.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>

Hi Miaohe,

This bug sounds relatively serious to me, and it seems old, so is it worth
sending to -stable?

Thanks,
Naoya Horiguchi