On Tue, Jan 19, 2021 at 6:26 PM Vincenzo Frascino <vincenzo.frasc...@arm.com> wrote: > > With the introduction of KASAN_HW_TAGS, kasan_report() dereferences > the address passed as a parameter. > > Add a comment to make sure that the preconditions to the function are > explicitly clarified. > > Note: An invalid address (e.g. NULL pointer address) passed to the > function when, KASAN_HW_TAGS is enabled, leads to a kernel panic. > > Cc: Andrey Ryabinin <aryabi...@virtuozzo.com> > Cc: Alexander Potapenko <gli...@google.com> > Cc: Dmitry Vyukov <dvyu...@google.com> > Cc: Leon Romanovsky <leo...@mellanox.com> > Cc: Andrey Konovalov <andreyk...@google.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@arm.com> > --- > mm/kasan/report.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index c0fb21797550..2485b585004d 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -403,6 +403,17 @@ static void __kasan_report(unsigned long addr, size_t > size, bool is_write, > end_report(&flags); > } > > +/** > + * kasan_report - report kasan fault details > + * @addr: valid address of the allocation where the tag fault was detected > + * @size: size of the allocation where the tag fault was detected > + * @is_write: the instruction that caused the fault was a read or write? > + * @ip: pointer to the instruction that cause the fault > + * > + * Note: When CONFIG_KASAN_HW_TAGS is enabled kasan_report() dereferences > + * the address to access the tags, hence it must be valid at this point in > + * order to not cause a kernel panic. > + */
It doesn't dereference the address, it just checks the tags, right? Ideally, kasan_report() should survive that with HW_TAGS like with the other modes. The reason it doesn't is probably because of a blank addr_has_metadata() definition for HW_TAGS in mm/kasan/kasan.h. I guess we should somehow check that the memory comes from page_alloc or kmalloc. Or otherwise make sure that it has tags. Maybe there's an arm instruction to check whether the memory has tags?