From a2f11547052001bd448ccec81dd1e68409078fbb Mon Sep 17 00:00:00 2001 From: Matthew Maurer Date: Tue, 20 Aug 2024 19:48:59 +0000 Subject: [PATCH] kasan: rust: Add KASAN smoke test via UAF Adds a smoke test to ensure that KASAN in Rust is actually detecting a Rust-native UAF. There is significant room to expand this test suite, but this will at least ensure that flags are having the intended effect. The rename from kasan_test.c to kasan_test_c.c is in order to allow the single kasan_test.ko test suite to contain both a .o file produced by the C compiler and one produced by rustc. Signed-off-by: Matthew Maurer Reviewed-by: Andrey Konovalov Link: https://lore.kernel.org/r/20240820194910.187826-5-mmaurer@google.com [ Applied empty line nit, removed double empty line, applied `rustfmt` and formatted crate comment. - Miguel ] Signed-off-by: Miguel Ojeda --- mm/kasan/Makefile | 8 +++++++- mm/kasan/kasan.h | 6 ++++++ mm/kasan/{kasan_test.c => kasan_test_c.c} | 11 +++++++++++ mm/kasan/kasan_test_rust.rs | 21 +++++++++++++++++++++ 4 files changed, 45 insertions(+), 1 deletion(-) rename mm/kasan/{kasan_test.c => kasan_test_c.c} (99%) create mode 100644 mm/kasan/kasan_test_rust.rs diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile index 7634dd2a6128..b88543e5c0cc 100644 --- a/mm/kasan/Makefile +++ b/mm/kasan/Makefile @@ -44,7 +44,8 @@ ifndef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX CFLAGS_KASAN_TEST += -fno-builtin endif -CFLAGS_kasan_test.o := $(CFLAGS_KASAN_TEST) +CFLAGS_kasan_test_c.o := $(CFLAGS_KASAN_TEST) +RUSTFLAGS_kasan_test_rust.o := $(RUSTFLAGS_KASAN) CFLAGS_kasan_test_module.o := $(CFLAGS_KASAN_TEST) obj-y := common.o report.o @@ -52,5 +53,10 @@ obj-$(CONFIG_KASAN_GENERIC) += init.o generic.o report_generic.o shadow.o quaran obj-$(CONFIG_KASAN_HW_TAGS) += hw_tags.o report_hw_tags.o tags.o report_tags.o obj-$(CONFIG_KASAN_SW_TAGS) += init.o report_sw_tags.o shadow.o sw_tags.o tags.o report_tags.o +kasan_test-objs := kasan_test_c.o +ifdef CONFIG_RUST + kasan_test-objs += kasan_test_rust.o +endif + obj-$(CONFIG_KASAN_KUNIT_TEST) += kasan_test.o obj-$(CONFIG_KASAN_MODULE_TEST) += kasan_test_module.o diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index fb2b9ac0659a..f438a6cdc964 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -555,6 +555,12 @@ static inline bool kasan_arch_is_ready(void) { return true; } void kasan_kunit_test_suite_start(void); void kasan_kunit_test_suite_end(void); +#ifdef CONFIG_RUST +char kasan_test_rust_uaf(void); +#else +static inline char kasan_test_rust_uaf(void) { return '\0'; } +#endif + #else /* CONFIG_KASAN_KUNIT_TEST */ static inline void kasan_kunit_test_suite_start(void) { } diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test_c.c similarity index 99% rename from mm/kasan/kasan_test.c rename to mm/kasan/kasan_test_c.c index 7b32be2a3cf0..0fd445a3be1c 100644 --- a/mm/kasan/kasan_test.c +++ b/mm/kasan/kasan_test_c.c @@ -1899,6 +1899,16 @@ static void match_all_mem_tag(struct kunit *test) kfree(ptr); } +/* + * Check that Rust performing a use-after-free using `unsafe` is detected. + * This is a smoke test to make sure that Rust is being sanitized properly. + */ +static void rust_uaf(struct kunit *test) +{ + KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_RUST); + KUNIT_EXPECT_KASAN_FAIL(test, kasan_test_rust_uaf()); +} + static struct kunit_case kasan_kunit_test_cases[] = { KUNIT_CASE(kmalloc_oob_right), KUNIT_CASE(kmalloc_oob_left), @@ -1971,6 +1981,7 @@ 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(rust_uaf), {} }; diff --git a/mm/kasan/kasan_test_rust.rs b/mm/kasan/kasan_test_rust.rs new file mode 100644 index 000000000000..caa7175964ef --- /dev/null +++ b/mm/kasan/kasan_test_rust.rs @@ -0,0 +1,21 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Helper crate for KASAN testing. +//! +//! Provides behavior to check the sanitization of Rust code. + +use core::ptr::addr_of_mut; +use kernel::prelude::*; + +/// Trivial UAF - allocate a big vector, grab a pointer partway through, +/// drop the vector, and touch it. +#[no_mangle] +pub extern "C" fn kasan_test_rust_uaf() -> u8 { + let mut v: Vec = Vec::new(); + for _ in 0..4096 { + v.push(0x42, GFP_KERNEL).unwrap(); + } + let ptr: *mut u8 = addr_of_mut!(v[2048]); + drop(v); + unsafe { *ptr } +}