Re: [PATCH mm] kasan: print virtual mapping info in reports

[Andrey Konovalov <andreyknvl@gmail.com>]

On Wed, Feb 16, 2022 at 8:31 PM Marco Elver <elver@google.com> wrote:
>
> On Wed, 16 Feb 2022 at 20:01, <andrey.konovalov@linux.dev> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Print virtual mapping range and its creator in reports affecting virtual
> > mappings.
> >
> > Also get physical page pointer for such mappings, so page information
> > gets printed as well.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >
> > ---
> >
> > Note: no need to merge this patch into any of the KASAN vmalloc patches
> > that are already in mm, better to keep it separate.
> > ---
> >  mm/kasan/report.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 137c2c0b09db..8002fb3c417d 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
> >                 pr_err(" %pS\n", addr);
> >         }
> >
> > +       if (is_vmalloc_addr(addr)) {
> > +               struct vm_struct *va = find_vm_area(addr);
> > +
> > +               pr_err("The buggy address belongs to the virtual mapping at\n"
> > +                      " [%px, %px) created by:\n"
> > +                      " %pS\n", va->addr, va->addr + va->size, va->caller);
>
> Can you show an example of what this looks like?

[   20.883723] The buggy address belongs to the virtual mapping at
[   20.883723]  [ffff8000081c9000, ffff8000081cb000) created by:
[   20.883723]  vmalloc_oob+0xd8/0x4dc

> It's not showing a stack trace,

No, only a single frame.

> so why not continue the line and just say "... created by: %pS\n"

Putting it on a separate line makes the line lengths looks more balanced.

Also, printing a frame on a separate line is consistent with the rest
of KASAN reporting code.