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From:   Andrey Konovalov <andreyknvl@google.com>
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
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Cc:     Kostya Serebryany <kcc@google.com>,
        Evgeniy Stepanov <eugenis@google.com>,
        Lee Smith <Lee.Smith@arm.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
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        Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
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        Chintan Pandya <cpandya@codeaurora.org>,
        Vishwath Mohan <vishwath@google.com>,
        Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH v9 11/20] kasan, arm64: fix up fault handling logic
Date:   Fri, 21 Sep 2018 17:13:33 +0200
Message-Id: <a8169b3802dda203e717ecd9cdc40cc3fa86e7e5.1537542735.git.andreyknvl@google.com>
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show_pte in arm64 fault handling relies on the fact that the top byte of
a kernel pointer is 0xff, which isn't always the case with tag-based
KASAN.

This patch resets the top byte in show_pte.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/fault.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 50b30ff30de4..78328c864d01 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -32,6 +32,7 @@
 #include <linux/perf_event.h>
 #include <linux/preempt.h>
 #include <linux/hugetlb.h>
+#include <linux/kasan.h>
 
 #include <asm/bug.h>
 #include <asm/cmpxchg.h>
@@ -134,6 +135,8 @@ void show_pte(unsigned long addr)
 	pgd_t *pgdp;
 	pgd_t pgd;
 
+	addr = (unsigned long)kasan_reset_tag((void *)addr);
+
 	if (addr < TASK_SIZE) {
 		/* TTBR0 */
 		mm = current->active_mm;
-- 
2.19.0.444.g18242da7ef-goog