kasan, arm64: fix pointer tags in KASAN reports

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 for kernel pointers in do_tag_check_fault by
setting them to the same value as bit 55. Explicitly use __untagged_addr()
instead of untagged_addr(), as the latter doesn't affect TTBR1 addresses.

Fixes: 708192a5dbf3 ("arm64: expose FAR_EL1 tag bits in siginfo")
Fixes: 6e7084ddbfcb ("kasan, arm64: print report from tag fault handler")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://linux-review.googlesource.com/id/I9ced973866036d8679e8f4ae325de547eb969649
Link: https://lore.kernel.org/r/ff30b0afe6005fd046f9ac72bfb71822aedccd89.1610731872.git.andreyknvl@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 3c40da479899dbb667f427ce8206c52d35e0c16e..35d75c60e2b8df0ed065e6090082c498d25897f7 100644 (file)
--- 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 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;
 }