Re: [PATCH 18/20] objtool: Add UACCESS validation

From: Andrey Ryabinin
Date: Thu Mar 07 2019 - 15:16:04 EST

On 3/7/19 8:41 PM, Peter Zijlstra wrote:
> On Thu, Mar 07, 2019 at 08:33:26AM -0800, Linus Torvalds wrote:
>> On Thu, Mar 7, 2019 at 3:52 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>>> XXX: are we sure we want __memset marked AC-safe?
>> It's certainly one of the safer functions to call with AC set, but it
>> sounds wrong anyway. It's not like it's likely to leak kernel data
>> (most memset's are with 0, and even the non-zero ones I can't imagine
>> are sensitive - more like poison values etc).
>> What's the call site that made you go "just add __memset() to the list"?
> __asan_{,un}poinson_stack_memory()

These two can be called only with CONFIG_KASAN_EXTRA=y which
was removed very recently, so it should be safe to delete these functions.

> kasan_{,un}poison_shadow()
> __memset()