linux-kernel - [PATCH v5] mm: x86: instrument __get/__put_kernel

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Message-Id: <20240922145757.986887-1-snovitoll@gmail.com>
Date: Sun, 22 Sep 2024 19:57:57 +0500
From: Sabyrzhan Tasbolatov <snovitoll@...il.com>
To: andreyknvl@...il.com
Cc: akpm@...ux-foundation.org,
	bp@...en8.de,
	brauner@...nel.org,
	dave.hansen@...ux.intel.com,
	dhowells@...hat.com,
	dvyukov@...gle.com,
	glider@...gle.com,
	hpa@...or.com,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	mingo@...hat.com,
	ryabinin.a.a@...il.com,
	snovitoll@...il.com,
	tglx@...utronix.de,
	vincenzo.frascino@....com,
	x86@...nel.org
Subject: [PATCH v5] mm: x86: instrument __get/__put_kernel_nofault

Instrument copy_from_kernel_nofault(), copy_to_kernel_nofault(),
strncpy_from_kernel_nofault() where __put_kernel_nofault,
__get_kernel_nofault macros are used.

__get_kernel_nofault needs instrument_memcpy_before() which handles
KASAN, KCSAN checks for src, dst address, whereas for __put_kernel_nofault
macro, instrument_write() check should be enough as it's validated via
kmsan_copy_to_user() in instrument_put_user().

copy_from_to_kernel_nofault_oob() kunit test triggers 4 KASAN OOB
bug reports as expected, one for each copy_from/to_kernel_nofault call.

Reported-by: Andrey Konovalov <andreyknvl@...il.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=210505
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>
---
v3: changed kunit test from UAF to OOB case and git commit message.
v4: updated a grammar in git commit message.
v5: copy_from_to_kernel_nofault_oob() works only for x86 arch,
	remove instrument_get_user() from __get_user_size on
	!CONFIG_CC_HAS_ASM_GOTO_OUTPUT
---
 arch/x86/include/asm/uaccess.h |  3 +++
 mm/kasan/kasan_test.c          | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3a7755c1a441..e8e5185dd65c 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -620,6 +620,7 @@ do {									\
 
 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
 #define __get_kernel_nofault(dst, src, type, err_label)			\
+	instrument_memcpy_before(dst, src, sizeof(type));		\
 	__get_user_size(*((type *)(dst)), (__force type __user *)(src),	\
 			sizeof(type), err_label)
 #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
@@ -627,6 +628,7 @@ do {									\
 do {									\
 	int __kr_err;							\
 									\
+	instrument_memcpy_before(dst, src, sizeof(type));		\
 	__get_user_size(*((type *)(dst)), (__force type __user *)(src),	\
 			sizeof(type), __kr_err);			\
 	if (unlikely(__kr_err))						\
@@ -635,6 +637,7 @@ do {									\
 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
 
 #define __put_kernel_nofault(dst, src, type, err_label)			\
+	instrument_write(dst, sizeof(type));				\
 	__put_user_size(*((type *)(src)), (__force type __user *)(dst),	\
 			sizeof(type), err_label)
 
diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 567d33b493e2..c369a5b1c6a7 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -1944,6 +1944,28 @@ static void match_all_mem_tag(struct kunit *test)
 	kfree(ptr);
 }
 
+static void copy_from_to_kernel_nofault_oob(struct kunit *test)
+{
+	char *ptr;
+	char buf[128];
+	size_t size = sizeof(buf);
+
+	KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_X86);
+
+	ptr = kmalloc(size - KASAN_GRANULE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		copy_from_kernel_nofault(&buf[0], ptr, size));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		copy_from_kernel_nofault(ptr, &buf[0], size));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		copy_to_kernel_nofault(&buf[0], ptr, size));
+	KUNIT_EXPECT_KASAN_FAIL(test,
+		copy_to_kernel_nofault(ptr, &buf[0], size));
+	kfree(ptr);
+}
+
 static struct kunit_case kasan_kunit_test_cases[] = {
 	KUNIT_CASE(kmalloc_oob_right),
 	KUNIT_CASE(kmalloc_oob_left),
@@ -2017,6 +2039,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
 	KUNIT_CASE(match_all_not_assigned),
 	KUNIT_CASE(match_all_ptr_tag),
 	KUNIT_CASE(match_all_mem_tag),
+	KUNIT_CASE(copy_from_to_kernel_nofault_oob),
 	{}
 };
 
-- 
2.34.1