linux-kernel - [PATCH mm 18/22] kasan: add comment about UACCESS regions to kasan

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Message-Id: <1201ca3c2be42c7bd077c53d2e46f4a51dd1476a.1646237226.git.andreyknvl@google.com>
Date:   Wed,  2 Mar 2022 17:36:38 +0100
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm 18/22] kasan: add comment about UACCESS regions to kasan_report

From: Andrey Konovalov <andreyknvl@...gle.com>

Add a comment explaining why kasan_report() is the only reporting
function that uses user_access_save/restore().

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 mm/kasan/report.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 7915af810815..08631d873204 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -430,6 +430,11 @@ void kasan_report_invalid_free(void *ptr, unsigned long ip)
 	end_report(&flags, ptr);
 }
 
+/*
+ * kasan_report() is the only reporting function that uses
+ * user_access_save/restore(): kasan_report_invalid_free() cannot be called
+ * from a UACCESS region, and kasan_report_async() is not used on x86.
+ */
 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 			unsigned long ip)
 {
-- 
2.25.1