Re: [RFC v3 PATCH 5/5] x86: check VM_DEAD flag in page fault

[Laurent Dufour]

On 30/06/2018 00:39, Yang Shi wrote:
> Check VM_DEAD flag of vma in page fault handler, if it is set, trigger
> SIGSEGV.
> 
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/mm/fault.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 9a84a0d..3fd2da5 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1357,6 +1357,10 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
>  		bad_area(regs, error_code, address);
>  		return;
>  	}
> +	if (unlikely(vma->vm_flags & VM_DEAD)) {
> +		bad_area(regs, error_code, address);
> +		return;
> +	}

This will have to be done for all the supported architectures, what about doing
this check in handle_mm_fault() and return VM_FAULT_SIGSEGV ?

>  	if (error_code & X86_PF_USER) {
>  		/*
>  		 * Accessing the stack below %sp is always a bug.
>