[PATCH] net: untag pointer in sockptr_is_kernel

[Christoph Hellwig]

On Tue, Aug 11, 2020 at 06:27:04PM +0800, Miles Chen wrote:
> From: Miles Chen <miles.chen at mediatek.com>
> 
> sockptr_is_kernel() uses (sockptr.kernel >= TASK_SIZE) to tell
> if the pointer is kernel space or user space. When user space uses
> the "top byte ignored" feature such as HWAsan, we must untag
> the pointer before checking against TASK_SIZE.
> 
> sockptr_is_kernel() will view a tagged user pointer as a kernel pointer
> and use memcpy directly and causes a kernel crash.

Dave merged a patch from me to rever the optimized sockptr
implementation for now.  If we bring it back we should fold in your
fix.