Re: [PATCH v5 00/16] Enable Linear Address Space Separation support

[Alexander Shishkin]

Matthew Wilcox <willy@xxxxxxxxxxxxx> writes:

> On Mon, Oct 28, 2024 at 06:07:48PM +0200, Alexander Shishkin wrote:
> I lack the wit to read & understand these patches to answer this
> question, so I'll just ask it:

I was hoping they are readable and straightforward. Please, do point out
things that are not so, or not explained well enough, I'll fix them.

> What happens when the kernel does a NULL pointer dereference (due to a
> bug)?  It's not an attempt to access userspace, but it should result in
> a good bug report.  Normally this would be outside a STAC/CLAC region,
> but I suppose technically it could be within one.

Outside of STAC/CLAC there will be a message, see 13/16 or [0].  It
doesn't have helpful things like "if (address < PAGE_SIZE) printk("NULL
ptr deref\n);", but since it prints the address, I assumed it was
sufficient. Does this sound reasonable? Or is it preferrable to make it
look exactly like the !LASS NULL dereference?

Inside STAC/CLAC it should trigger a regular page fault and all the
error messages that result from it.

[0] https://lore.kernel.org/all/20241028160917.1380714-14-alexander.shishkin@xxxxxxxxxxxxxxx/

Thanks,
--
Alex