Re: [PATCH] vsprintf: sanely handle NULL passed to %pe

From: Petr Mladek
Date: Wed Feb 19 2020 - 09:46:03 EST

On Wed 2020-02-19 14:56:32, Rasmus Villemoes wrote:
> On 19/02/2020 14.48, Petr Mladek wrote:
> > On Wed 2020-02-19 12:53:22, Rasmus Villemoes wrote:
> >> --- a/lib/vsprintf.c
> >> +++ b/lib/vsprintf.c
> > The test should go into null_pointer() instead of errptr().
> Eh, no, the behaviour of %pe is tested by errptr(). I'll keep it that
> way. But I should add a #else section that tests how %pe behaves without
> CONFIG_SYMBOLIC_ERRNAME - though that's orthogonal to this patch.

OK, we should agree on some structure first.

We already have two top level functions that test how a particular
pointer is printed using different pointer modifiers:

null_pointer(); -> NULL with %p, %pX, %pE
invalid_pointer(); -> random pointer with %p, %pX, %pE

Following this logic, errptr() should test how a pointer from IS_ERR() range
is printed using different pointer formats.

I am open to crate another logic but it must be consistent.
If you want to check %pe with NULL in errptr(), you have to
split the other two functions per-modifier. IMHO, it is not
worth it.

Sigh, I should have been more strict[*]. The function should have been
called err_ptr() and located right below null_pointer().

[*] I am still trying to find a right balance between preventing
nitpicking, bikeshedding, enforcing my style, and creating a mess.

> > Could you send updated patch, please? ;-)
> I'll wait a day or two for more comments. It doesn't seem very urgent.


> >> BTW., your original patch for %p lacks corresponding update of
> >> test_vsprintf.c. Please add appropriate test cases.
> >
> > diff --git a/lib/test_printf.c b/lib/test_printf.c
> > index 2d9f520d2f27..1726a678bccd 100644
> > --- a/lib/test_printf.c
> > +++ b/lib/test_printf.c
> > @@ -333,7 +333,7 @@ test_hashed(const char *fmt, const void *p)
> > static void __init
> > null_pointer(void)
> > {
> > - test_hashed("%p", NULL);
> > + test(ZEROS "00000000", "%p", NULL);
> No, it most certainly also needs to check a few "%p", ERR_PTR(-4) cases
> (where one of course has to use explicit integers and not E* constants).

Yes, it would be great to add checks for %p, %px for IS_ERR() range.
But it is different story. The above change is for the original patch
and it was about NULL pointer handling.

Best Regards,