From: Wang Wensheng <wsw9603@163.com>
To: ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com,
	dvyukov@google.com, vincenzo.frascino@arm.com,
	akpm@linux-foundation.org, kasan-dev@googlegroups.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: wsw9603@163.com
Subject: [PATCH v2] kasan/test: only do kmalloc_double_kzfree for generic mode
Date: Sun, 24 May 2026 11:10:53 +0800	[thread overview]
Message-ID: <20260524031053.381776-1-wsw9603@163.com> (raw)

kmalloc_double_kzfree() would corrupt kernel memory when the just
freed memory were allocated by another thread before the second
call to kfree_sensitive() and the new allocation tag happened to
match the old one.

This could not happen in GENERIC mode as it uses quarantine.

Signed-off-by: Wang Wensheng <wsw9603@163.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
---
v1->v2:
Update comment suggested by Andrey Konovalov.
--
 mm/kasan/kasan_test_c.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
index 32d06cbf6a31..3f4ed29178b3 100644
--- a/mm/kasan/kasan_test_c.c
+++ b/mm/kasan/kasan_test_c.c
@@ -874,6 +874,16 @@ static void kmalloc_double_kzfree(struct kunit *test)
 	char *ptr;
 	size_t size = 16;
 
+	/*
+	 * With the tag-based KASAN modes, if the memory happens to be
+	 * reallocated between the two frees and the new allocation tag happens
+	 * to match the old one, the second free will cause a memory corruption.
+	 * Resolving https://bugzilla.kernel.org/show_bug.cgi?id=212177 would
+	 * help to deal with this. With Generic KASAN, it's effectively
+	 * impossible for the memory to get reallocated due to the quarantine.
+	 */
+	KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_GENERIC);
+
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
-- 
2.43.0

                 reply	other threads:[~2026-05-24  3:11 UTC|newest]

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