On Mon, May 31, 2021 at 6:59 PM Kuan-Ying Lee [off-list ref] wrote:

quoted

quoted

+config KASAN_HW_TAGS_IDENTIFY
+   bool "Enable memory corruption identification"
+   depends on KASAN_HW_TAGS
+   help
+     This option enables best-effort identification of bug type
+     (use-after-free or out-of-bounds) at the cost of increased
+     memory consumption.

Can we rename KASAN_SW_TAGS_IDENTIFY -> KASAN_TAGS_IDENTIFY in a
separate patch and then use that?

Or do we have a problem renaming this options if there are existing
users of it?

Using the single KASAN_TAGS_IDENTIFY config option is what I would like to see.

Since this is a purely debugging feature for a less popular KASAN
mode, I think renaming the config name is OK.

I tend to keep KASAN_SW_TAGS_IDENTIFY and KASAN_HW_TAGS_IDENTIFY
separately.

We need these two configs to decide how many stacks we will store.

You can define KASAN_NR_FREE_STACKS to different values depending on
whether HW_TAGS or SW_TAGS is in use. I don't see a problem here.

If we store as many stacks as SW tag-based kasan does(5 stacks), we might
mistake out-of-bound issues for use-after-free sometime. Becuase HW
tag-based kasan only has 16 kinds of tags. When Out-of-bound issues happened, it might
find the same tag in the stack we just stored and mistake happened.
There is high probability that this mistake will happen.