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SubjectRe: [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop
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On 8/27/19 11:41 AM, Jason Gunthorpe wrote:
> On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote:
>
>> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
>> mm/hmm.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/hmm.c b/mm/hmm.c
>> index 29371485fe94..4882b83aeccb 100644
>> +++ b/mm/hmm.c
>> @@ -292,6 +292,9 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
>> hmm_vma_walk->last = addr;
>> i = (addr - range->start) >> PAGE_SHIFT;
>>
>> + if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE))
>> + return -EPERM;
>
> Can walk->vma be NULL here? hmm_vma_do_fault() touches it
> unconditionally.
>
> Jason
>
walk->vma can be NULL. hmm_vma_do_fault() no longer touches it
unconditionally, that is what the preceding patch fixes.
I suppose I could change hmm_vma_walk_hole_() to check for NULL
and fill in the pfns[] array, I just chose to handle it in
hmm_vma_do_fault().

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