linux-kernel - [PATCH v3 2/2] kasan: Add explicit preconditions to kasan

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Date:   Fri, 22 Jan 2021 14:37:48 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com
Cc:     Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
the address passed as a parameter.

Add a comment to make sure that the preconditions to the function are
explicitly clarified.

Note: An invalid address (e.g. NULL) passed to the function when,
KASAN_HW_TAGS is enabled, leads to a kernel panic.

Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Leon Romanovsky <leonro@...lanox.com>
Cc: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
---
 include/linux/kasan.h | 7 +++++++
 mm/kasan/kasan.h      | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index fe1ae73ff8b5..0aea9e2a2a01 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
 	return (void *)arch_kasan_reset_tag(addr);
 }
 
+/**
+ * kasan_report - print a report about a bad memory access detected by KASAN
+ * @addr: address of the bad access
+ * @size: size of the bad access
+ * @is_write: whether the bad access is a write or a read
+ * @ip: instruction pointer for the accessibility check or the bad access itself
+ */
 bool kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cc4d9e1d49b1..8c706e7652f2 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
 
 static inline bool addr_has_metadata(const void *addr)
 {
-	return true;
+	return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
 }
 
 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
-- 
2.30.0