Re: [PATCH STABLE 4.9] x86, mm, gup: prevent get_page() race with munmap in paravirt guest

[Vlastimil Babka]

On 9/19/19 8:26 PM, Ben Hutchings wrote:
> On Mon, 2019-08-19 at 18:58 +0100, Vlastimil Babka wrote:
> [...]
>> Hi, I'm sending this stable-only patch for consideration because it's probably
>> unrealistic to backport the 4.13 switch to generic GUP. I can look at 4.4 and
>> 3.16 if accepted. The RCU page table freeing could be also considered.
> 
> I would be interested in backports for 3.16 and 4.4.
> 
>> Note the patch also includes page refcount protection. I found out that
>> 8fde12ca79af ("mm: prevent get_user_pages() from overflowing page refcount")
>> backport to 4.9 missed the arch-specific gup implementations:
>> https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@xxxxxxx/
> [...]
> 
> I suppose that still needs to be addressed for 4.9, right?

Here's what is AFAIK missing for 4.9 for x86 and s390.

----8<----