Re: [Intel-gfx] [PATCH v2] drm/i915/userptr: restore probe_range behaviour

[Andrzej Hajda <andrzej.hajda@intel.com>]

On 28.10.2022 15:06, Matthew Auld wrote:
> The conversion looks harmless, however the addr value is updated inside
> the loop with the previous vm_end, which then incorrectly leads to
> for_each_vma_range() iterating over stuff outside the range we care
> about. Fix this by storing the end value separately. Also fix the case
> where the range doesn't intersect with any vma, or if the vma itself
> doesn't extend the entire range, which must mean we have hole at the
> end. Both should result in an error, as per the previous behaviour.
> 
> v2: Fix the cases where the range is empty, or if there's a hole at
> the end of the range
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7247
> Testcase: igt@gem_userptr_blits@probe
> Fixes: f683b9d61319 ("i915: use the VMA iterator")
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Yu Zhao <yuzhao@google.com>

Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>

Regards
Andrzej

> ---
>   drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 1b1a22716722..ca7a388ba2bf 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -427,9 +427,10 @@ probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
>   {
>   	VMA_ITERATOR(vmi, mm, addr);
>   	struct vm_area_struct *vma;
> +	unsigned long end = addr + len;
>   
>   	mmap_read_lock(mm);
> -	for_each_vma_range(vmi, vma, addr + len) {
> +	for_each_vma_range(vmi, vma, end) {
>   		/* Check for holes, note that we also update the addr below */
>   		if (vma->vm_start > addr)
>   			break;
> @@ -441,7 +442,7 @@ probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
>   	}
>   	mmap_read_unlock(mm);
>   
> -	if (vma)
> +	if (vma || addr < end)
>   		return -EFAULT;
>   	return 0;
>   }