linux-kernel - [PATCH v2 2/2] kasan: Add explicit preconditions to kasan

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Message-Id: <20210121131956.23246-3-vincenzo.frascino@arm.com>
Date:   Thu, 21 Jan 2021 13:19:56 +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>
Subject: [PATCH v2 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>
---
 mm/kasan/kasan.h  | 2 +-
 mm/kasan/report.c | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

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 */
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index c0fb21797550..8b690091cb37 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -403,6 +403,13 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 	end_report(&flags);
 }
 
+/**
+ * kasan_report - report kasan fault details
+ * @addr: valid address of the allocation where the tag fault was detected
+ * @size: size of the allocation where the tag fault was detected
+ * @is_write: the instruction that caused the fault was a read or write?
+ * @ip: pointer to the instruction that cause the fault
+ */
 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 			unsigned long ip)
 {
-- 
2.30.0