On Wed, Jun 10, 2020 at 04:39:44PM +0530, Shyam Thombre wrote: > KASAN sw tagging sets a random tag of 8 bits in the top byte of the pointer > returned by the memory allocating functions. So for the functions unaware > of this change, the top 8 bits of the address must be reset which is done > by the function arch_kasan_reset_tag(). > > Signed-off-by: Shyam Thombre <sthom...@codeaurora.org> > --- > arch/arm64/mm/mmu.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index e7fbc62..eae7655 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -723,6 +723,7 @@ int kern_addr_valid(unsigned long addr) > pmd_t *pmdp, pmd; > pte_t *ptep, pte; > > + addr = arch_kasan_reset_tag(addr); > if ((((long)addr) >> VA_BITS) != -1UL) > return 0;
It would be interesting to know what fails without this patch. The only user seems to be read_kcore() and, at a quick look, I don't see how it can generate tagged addresses. -- Catalin
