Re: [PATCH] lib/vsprintf: Validate sleepable context during restrictred pointer formatting

[Thomas Weißschuh]

On Tue, Mar 17, 2026 at 04:07:56PM +0200, Andy Shevchenko wrote:
> On Tue, Mar 17, 2026 at 12:41:23PM +0100, Thomas Weißschuh wrote:
> > Depending on the system configuration, the restricted pointer formatting
> > might call into the security subsystem which might sleep.
> > As %pK is intended to be only used from read handlers of virtual files,
> > which always run in task context, this should never happen in practice.
> > However, developers have used %pK before from atomic context without
> > realizing this restriction. While all existing user of %pK through
> > printk() have been removed, new ones might be reintroduced accidentally
> > in the future.
> > 
> > Add a might_sleep(), so that misuse of %pK from atomic context is
> > detected right away.
> 
> ...
> 
> > +	/* Only usable from task context, The call to has_capability_noaudit() might sleep. */
> > +	might_sleep();
> 
> Yeah, but for kptr_restrict != 1 it's not true. Perhaps might_sleep_if() ?

kptr_restrict can change any time at runtime. The whole point of this patch
is to detect the API misuse independently from the system configuration.
Developers probably don't test against kptr_restrict == 1 and therefore
it will only blow up on users system.


Thomas