# \[PATCH 2/2\] kasan, arm64: fix pointer tags in KASAN reports

- From: Andrey Konovalov \<hidden\>
- Date: 2021-01-13 16:04:50 
- List: linux-arm-kernel
- Page: https://ratatoskr.run/linux-arm-kernel/2021/01/6233583
- Thread: https://ratatoskr.run/linux-arm-kernel/2021/01/6233581/t.md

```text
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 <redacted>
---
 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);
 	/*
 	 * SAS bits aren't set for all faults reported in EL1, so we can't
 	 * find out access size.
-- 
2.30.0.284.gd98b1dd5eaa7-goog


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```