Commit 811808d3 authored by Nirjhar Roy's avatar Nirjhar Roy Committed by Andrew Morton
Browse files

mm/kfence: add a new kunit test test_use_after_free_read_nofault() 

Faults from copy_from_kernel_nofault() need to be handled by fixup table
and should not be handled by kfence.  Otherwise while reading /proc/kcore
which uses copy_from_kernel_nofault(), kfence can generate false
negatives.  This can happen when /proc/kcore ends up reading an unmapped
address from kfence pool.

Let's add a testcase to cover this case.

Link: https://lkml.kernel.org/r/210e561f7845697a32de44b643393890f180069f.1729272697.git.ritesh.list@gmail.com


Signed-off-by: default avatarNirjhar Roy <nirjhar@linux.ibm.com>
Co-developed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Tested-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f364cdeb

mm/kfence/kfence_test.c

+17 −0
Original line number Diff line number Diff line
@@ -383,6 +383,22 @@ static void test_use_after_free_read(struct kunit *test) 
	KUNIT_EXPECT_TRUE(test, report_matches(&expect));

}



static void test_use_after_free_read_nofault(struct kunit *test)

{

	const size_t size = 32;

	char *addr;

	char dst;

	int ret;



	setup_test_cache(test, size, 0, NULL);

	addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);

	test_free(addr);

	/* Use after free with *_nofault() */

	ret = copy_from_kernel_nofault(&dst, addr, 1);

	KUNIT_EXPECT_EQ(test, ret, -EFAULT);

	KUNIT_EXPECT_FALSE(test, report_available());

}



static void test_double_free(struct kunit *test)

{

	const size_t size = 32;
@@ -780,6 +796,7 @@ static struct kunit_case kfence_test_cases[] = { 
	KFENCE_KUNIT_CASE(test_out_of_bounds_read),

	KFENCE_KUNIT_CASE(test_out_of_bounds_write),

	KFENCE_KUNIT_CASE(test_use_after_free_read),

	KFENCE_KUNIT_CASE(test_use_after_free_read_nofault),

	KFENCE_KUNIT_CASE(test_double_free),

	KFENCE_KUNIT_CASE(test_invalid_addr_free),

	KFENCE_KUNIT_CASE(test_corruption),