On 21.11.24 14:44, David Hildenbrand wrote:
On 21.11.24 13:41, Jeongjun Park wrote:vma_adjust_trans_huge() uses find_vma() to get the VMA, but find_vma() uses the returned pointer without any verification, even though it may return NULL. In this case, NULL pointer dereference may occur, so to prevent this, vma_adjust_trans_huge() should be fix to verify the return value of find_vma(). Cc: <stable@xxxxxxxxxxxxxxx> Fixes: 685405020b9f ("mm/khugepaged: stop using vma linked list")If that's an issue, wouldn't it have predated that commit? struct vm_area_struct *next = vma->vm_next; unsigned long nstart = next->vm_start; Would have also assumed that there is a next VMA that can be dereferenced, no?
And looking into the details, we only assume that there is a next VMA if we are explicitly told to by the caller of vma_adjust_trans_huge() using "adjust_next".
There is only one such caller, vma_merge_existing_range()->commit_merge() where we set adj_start -> "adjust_next" where we seem to have a guarantee that there is a next VMA.
So I don't think there is an issue here (although the code does look confusing ...).
Not sure, though, if a if (WARN_ON_ONCE(!next)) return; would be reasonable. -- Cheers, David / dhildenb
