On Thu, Jun 06, 2019 at 12:27:40PM +0100, Catalin Marinas wrote: > On Thu, Jun 06, 2019 at 10:24:01AM +0530, Anshuman Khandual wrote: > > On 06/04/2019 08:26 PM, Catalin Marinas wrote: > > > On Mon, Jun 03, 2019 at 12:11:25PM +0530, Anshuman Khandual wrote: > > >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > > >> index 4bb65f3..41fa905 100644 > > >> --- a/arch/arm64/mm/fault.c > > >> +++ b/arch/arm64/mm/fault.c > > >> @@ -397,37 +397,29 @@ static void do_bad_area(unsigned long addr, > > >> unsigned int esr, struct pt_regs *re > > >> static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long > > >> addr, > > >> unsigned int mm_flags, unsigned long > > >> vm_flags) > > >> { > > >> - struct vm_area_struct *vma; > > >> - vm_fault_t fault; > > >> + struct vm_area_struct *vma = find_vma(mm, addr); > > >> > > >> - vma = find_vma(mm, addr); > > >> - fault = VM_FAULT_BADMAP; > > >> if (unlikely(!vma)) > > >> - goto out; > > >> - if (unlikely(vma->vm_start > addr)) > > >> - goto check_stack; > > >> + return VM_FAULT_BADMAP; > > >> > > >> /* > > >> * Ok, we have a good vm_area for this memory access, so we can > > >> handle > > >> * it. > > >> */ > > >> -good_area: > > >> + if (unlikely(vma->vm_start > addr)) { > > >> + if (!(vma->vm_flags & VM_GROWSDOWN)) > > >> + return VM_FAULT_BADMAP; > > >> + if (expand_stack(vma, addr)) > > >> + return VM_FAULT_BADMAP; > > >> + } > > > > > > You could have a single return here: > > > > > > if (unlikely(vma->vm_start > addr) && > > > (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, addr))) > > > return VM_FAULT_BADMAP; > > > > > > Not sure it's any clearer though. > > > > TBH the proposed one seems clearer as it separates effect (vma->vm_start > > > addr) > > from required permission check (vma->vm_flags & VM_GROWSDOWN) and required > > action > > (expand_stack(vma, addr)). But I am happy to change as you have mentioned > > if that > > is preferred. > > Not bothered really. You can leave them as in your proposal (I was just > seeing the VM_GROWSDOWN check tightly coupled with the expand_stack(), > it's fine either way).
Personally, I find it clearer as separate statements, so I'd suggest keeping it as per Anshuman's proposal. Thanks, Mark.