The quilt patch titled Subject: mm, kasan, kmsan: instrument copy_from/to_kernel_nofault has been removed from the -mm tree. Its filename was mm-kasan-kmsan-copy_from-to_kernel_nofault.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx> Subject: mm, kasan, kmsan: instrument copy_from/to_kernel_nofault Date: Fri, 11 Oct 2024 08:53:10 +0500 Instrument copy_from_kernel_nofault() with KMSAN for uninitialized kernel memory check and copy_to_kernel_nofault() with KASAN, KCSAN to detect the memory corruption. syzbot reported that bpf_probe_read_kernel() kernel helper triggered KASAN report via kasan_check_range() which is not the expected behaviour as copy_from_kernel_nofault() is meant to be a non-faulting helper. Solution is, suggested by Marco Elver, to replace KASAN, KCSAN check in copy_from_kernel_nofault() with KMSAN detection of copying uninitilaized kernel memory. In copy_to_kernel_nofault() we can retain instrument_write() explicitly for the memory corruption instrumentation. copy_to_kernel_nofault() is tested on x86_64 and arm64 with CONFIG_KASAN_SW_TAGS. On arm64 with CONFIG_KASAN_HW_TAGS, kunit test currently fails. Need more clarification on it. [akpm@xxxxxxxxxxxxxxxxxxxx: fix comment layout, per checkpatch Link: https://lore.kernel.org/linux-mm/CANpmjNMAVFzqnCZhEity9cjiqQ9CVN1X7qeeeAp_6yKjwKo8iw@xxxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/20241011035310.2982017-1-snovitoll@xxxxxxxxx Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> Reported-by: syzbot+61123a5daeb9f7454599@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=61123a5daeb9f7454599 Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=210505 Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> [KASAN] Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> [KASAN] Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kasan/kasan_test_c.c | 36 ++++++++++++++++++++++++++++++++++++ mm/kmsan/kmsan_test.c | 17 +++++++++++++++++ mm/maccess.c | 10 ++++++++-- 3 files changed, 61 insertions(+), 2 deletions(-) --- a/mm/kasan/kasan_test_c.c~mm-kasan-kmsan-copy_from-to_kernel_nofault +++ a/mm/kasan/kasan_test_c.c @@ -1928,6 +1928,41 @@ static void rust_uaf(struct kunit *test) KUNIT_EXPECT_KASAN_FAIL(test, kasan_test_rust_uaf()); } +static void copy_to_kernel_nofault_oob(struct kunit *test) +{ + char *ptr; + char buf[128]; + size_t size = sizeof(buf); + + /* + * This test currently fails with the HW_TAGS mode. The reason is + * unknown and needs to be investigated. + */ + KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_HW_TAGS); + + ptr = kmalloc(size - KASAN_GRANULE_SIZE, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + OPTIMIZER_HIDE_VAR(ptr); + + /* + * We test copy_to_kernel_nofault() to detect corrupted memory that is + * being written into the kernel. In contrast, + * copy_from_kernel_nofault() is primarily used in kernel helper + * functions where the source address might be random or uninitialized. + * Applying KASAN instrumentation to copy_from_kernel_nofault() could + * lead to false positives. By focusing KASAN checks only on + * copy_to_kernel_nofault(), we ensure that only valid memory is + * written to the kernel, minimizing the risk of kernel corruption + * while avoiding false positives in the reverse case. + */ + 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), @@ -2000,6 +2035,7 @@ static struct kunit_case kasan_kunit_tes KUNIT_CASE(match_all_not_assigned), KUNIT_CASE(match_all_ptr_tag), KUNIT_CASE(match_all_mem_tag), + KUNIT_CASE(copy_to_kernel_nofault_oob), KUNIT_CASE(rust_uaf), {} }; --- a/mm/kmsan/kmsan_test.c~mm-kasan-kmsan-copy_from-to_kernel_nofault +++ a/mm/kmsan/kmsan_test.c @@ -640,6 +640,22 @@ static void test_unpoison_memory(struct KUNIT_EXPECT_TRUE(test, report_matches(&expect)); } +static void test_copy_from_kernel_nofault(struct kunit *test) +{ + long ret; + char buf[4], src[4]; + size_t size = sizeof(buf); + + EXPECTATION_UNINIT_VALUE_FN(expect, "copy_from_kernel_nofault"); + kunit_info( + test, + "testing copy_from_kernel_nofault with uninitialized memory\n"); + + ret = copy_from_kernel_nofault((char *)&buf[0], (char *)&src[0], size); + USE(ret); + KUNIT_EXPECT_TRUE(test, report_matches(&expect)); +} + static struct kunit_case kmsan_test_cases[] = { KUNIT_CASE(test_uninit_kmalloc), KUNIT_CASE(test_init_kmalloc), @@ -664,6 +680,7 @@ static struct kunit_case kmsan_test_case KUNIT_CASE(test_long_origin_chain), KUNIT_CASE(test_stackdepot_roundtrip), KUNIT_CASE(test_unpoison_memory), + KUNIT_CASE(test_copy_from_kernel_nofault), {}, }; --- a/mm/maccess.c~mm-kasan-kmsan-copy_from-to_kernel_nofault +++ a/mm/maccess.c @@ -13,9 +13,14 @@ bool __weak copy_from_kernel_nofault_all return true; } +/* + * The below only uses kmsan_check_memory() to ensure uninitialized kernel + * memory isn't leaked. + */ #define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \ while (len >= sizeof(type)) { \ - __get_kernel_nofault(dst, src, type, err_label); \ + __get_kernel_nofault(dst, src, type, err_label); \ + kmsan_check_memory(src, sizeof(type)); \ dst += sizeof(type); \ src += sizeof(type); \ len -= sizeof(type); \ @@ -49,7 +54,8 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofau #define copy_to_kernel_nofault_loop(dst, src, len, type, err_label) \ while (len >= sizeof(type)) { \ - __put_kernel_nofault(dst, src, type, err_label); \ + __put_kernel_nofault(dst, src, type, err_label); \ + instrument_write(dst, sizeof(type)); \ dst += sizeof(type); \ src += sizeof(type); \ len -= sizeof(type); \ _ Patches currently in -mm which might be from snovitoll@xxxxxxxxx are kasan-move-checks-to-do_strncpy_from_user.patch kasan-migrate-copy_user_test-to-kunit.patch kasan-delete-config_kasan_module_test.patch kasan-delete-config_kasan_module_test-fix.patch kasan-use-export_symbol_if_kunit-to-export-symbols.patch kasan-change-kasan_atomics-kunit-test-as-kunit_case_slow.patch