Re: [PATCH v13 12/20] uprobes, arm64: untag user pointers in find_active_uprobe

[Catalin Marinas <catalin.marinas@arm.com>]

On Wed, Mar 20, 2019 at 03:51:26PM +0100, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
> 
> find_active_uprobe() uses user pointers (obtained via
> instruction_pointer(regs)) for vma lookups, which can only by done with
> untagged pointers.
> 
> Untag user pointers in this function.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  kernel/events/uprobes.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index c5cde87329c7..d3a2716a813a 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1992,6 +1992,8 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
>  	struct uprobe *uprobe = NULL;
>  	struct vm_area_struct *vma;
>  
> +	bp_vaddr = untagged_addr(bp_vaddr);
> +
>  	down_read(&mm->mmap_sem);
>  	vma = find_vma(mm, bp_vaddr);
>  	if (vma && vma->vm_start <= bp_vaddr) {

Similarly here, that's a breakpoint address, hence instruction pointer
(PC) which is untagged.

-- 
Catalin