RE: [PATCH V11 4/5] vsprintf: add printk specifier %px

From: Kees Cook

Sent: 29 November 2017 22:28
On Wed, Nov 29, 2017 at 2:07 AM, David Laight [off-list ref] wrote:

quoted

From: Linus Torvalds

quoted

Sent: 29 November 2017 02:29

On Tue, Nov 28, 2017 at 6:05 PM, Tobin C. Harding [off-list ref] wrote:

quoted

   Let's add specifier %px as a
clear, opt-in, way to print a pointer and maintain some level of
isolation from all the other hex integer output within the Kernel.

Yes, I like this model. It's easy and it's obvious ("'x' for hex"),
and it gives people a good way to say "yes, I really want the actual
address as hex" for if/when the hashed pointer doesn't work for some
reason.

Remind me to change every %p to %px on kernels that support it.

Although the absolute values of pointers may not be useful, knowing
that two pointer differ by a small amount is useful.
It is also useful to know whether pointers are to stack, code, static
data or heap.

This change to %p is going to make debugging a nightmare.

In the future, maybe we could have a knob: unhashed, hashed (default),
or zeroed.

Add a 4th, hashed_page+offset.

Isn't there already a knob for %pK, bits in the same value could be used.
That would make it easy to ensure that %pK is more restructive than %p.

	David