Re: [PATCH] linux-user: Ensure mmap_min_addr is non-zero

[Richard Henderson]

On 7/27/20 4:19 AM, Laurent Vivier wrote:
> Le 24/07/2020 à 23:23, Richard Henderson a écrit :
>> When the chroot does not have /proc mounted, we can read neither
>> /proc/sys/vm/mmap_min_addr nor /proc/sys/maps.
>>
>> The enforcement of mmap_min_addr in the host kernel is done by
>> the security module, and so does not apply to processes owned
>> by root.  Which leads pgd_find_hole_fallback to succeed in probing
>> a reservation at address 0.  Which confuses pgb_reserved_va to
>> believe that guest_base has not actually been initialized.
>>
>> We don't actually want NULL addresses to become accessible, so
>> make sure that mmap_min_addr is initialized with a non-zero value.
>>
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1888728
>> Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>  linux-user/main.c | 16 ++++++++++++++--
>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>
> 
> Richard, do you want to add this fix in one of your branches PR?

I don't have anything queued at the moment.  I thought I would be able to
convince Alex to add it to his misc queue, but he sent that this morning.

> In this case:
> Acked-by: Laurent Vivier <laurent@vivier.eu>
> 
> Otherwise I can prepare a small one for linux-user, adding one or two
> fixes...

Please go ahead.


r~