On Wed, Jan 13, 2021 at 5:54 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Wed, Jan 13, 2021 at 05:03:30PM +0100, Andrey Konovalov wrote: > > As of the "arm64: expose FAR_EL1 tag bits in siginfo" patch, the address > > that is passed to report_tag_fault has pointer tags in the format of 0x0X, > > while KASAN uses 0xFX format (note the difference in the top 4 bits). > > > > Fix up the pointer tag before calling kasan_report. > > > > Link: https://linux-review.googlesource.com/id/I9ced973866036d8679e8f4ae325de547eb969649 > > Fixes: dceec3ff7807 ("arm64: expose FAR_EL1 tag bits in siginfo") > > Fixes: 4291e9ee6189 ("kasan, arm64: print report from tag fault handler") > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > --- > > arch/arm64/mm/fault.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > > index 3c40da479899..a218f6f2fdc8 100644 > > --- a/arch/arm64/mm/fault.c > > +++ b/arch/arm64/mm/fault.c > > @@ -304,6 +304,8 @@ static void report_tag_fault(unsigned long addr, unsigned int esr, > > { > > bool is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0; > > > > + /* The format of KASAN tags is 0xF<x>. */ > > + addr |= (0xF0UL << MTE_TAG_SHIFT); > > Ah, I see, that top 4 bits are zeroed by do_tag_check_fault(). When this > was added, the only tag faults were generated for user addresses. > > Anyway, I'd rather fix it in there based on bit 55, something like (only > compile-tested): > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 3c40da479899..2b71079d2d32 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -709,10 +709,11 @@ static int do_tag_check_fault(unsigned long far, unsigned int esr, > struct pt_regs *regs) > { > /* > - * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag > - * check faults. Mask them out now so that userspace doesn't see them. > + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN > + * for tag check faults. Set them to the corresponding bits in the > + * untagged address. > */ > - far &= (1UL << 60) - 1; > + far = (untagged_addr(far) & ~MTE_TAG_MASK) | (far & MTE_TAG_MASK) ; > do_bad_area(far, esr, regs); > return 0; > } BTW, we can do "untagged_addr(far) | (far & MTE_TAG_MASK)" here, as untagged_addr() doesn't change kernel pointers.
