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charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jan 15, 2021 at 4:07 PM Catalin Marinas wrote: > > On Fri, Jan 15, 2021 at 02:12:24PM +0100, Andrey Konovalov wrote: > > On Wed, Jan 13, 2021 at 5:54 PM Catalin Marinas 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 > > > > --- > > > > 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. */ > > > > + 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; > > > } > > > > Sounds good, will do in v3, thanks! > > I wonder if this one gives the same result (so please check): > > far = u64_replace_bits(untagged_addr(far), far, MTE_TAG_MASK); > > (defined in linux/bitfield.h) No, it zeroes out the tag. Not sure why. I took a brief look at the implementation and didn't get how it's supposed to work - too much bit trickery.