Hi. This is a third iteration of kerenel address sanitizer (KASan). KASan is a runtime memory debugger designed to find use-after-free and out-of-bounds bugs. Currently KASAN supported only for x86_64 architecture and requires kernel to be build with SLUB allocator. KASAN uses compile-time instrumentation for checking every memory access, therefore you will need a fresh GCC >= v5.0.0. Patches are based on mmotm-2014-09-22-16-57 tree and also avaliable in git: git://github.com/aryabinin/linux --branch=kasan/kasan_v3 Note: patch (https://lkml.org/lkml/2014/9/4/364) for gcc5 support somewhat just disappeared from the last mmotm, so you will need to apply it. It's already done in my git above. Changes since v2: - Shadow moved to vmalloc area. - Added posion page. This page mapped to shadow correspondig to shadow region itself: [kasan_mem_to_shadow(KASAN_SHADOW_START) - kasan_mem_to_shadow(KASAN_SHADOW_END)] It used to catch memory access to shadow outside mm/kasan/. - Fixed boot with CONFIG_DEBUG_VIRTUAL=y - Fixed boot with KASan and stack protector enabled (patch "x86_64: load_percpu_segment: read irq_stack_union.gs_base before load_segment") - Fixed build with CONFIG_EFI_STUB=y - Some slub specific stuf moved from mm/slab.h to include/linux/slub_def.h - Fixed Kconfig dependency. CONFIG_KASAN depends on CONFIG_SLUB_DEBUG. - Optimizations of __asan_load/__asan_store. - Spelling fixes from Randy. - Misc minor cleanups in different places. - Added inline instrumentation in last patch. This will require two not yet-in-trunk-patches for GCC: https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00452.html https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00605.html Changes since v1: - The main change is in shadow memory laoyut. Now for shadow memory we reserve 1/8 of all virtual addresses available for kernel. 16TB on x86_64 to cover all 128TB of kernel's address space. At early stage we map whole shadow region with zero page. Latter, after physical memory mapped to direct mapping address range we unmap zero pages from corresponding shadow and allocate and map a real memory. - Since per-arch work is much bigger now, support for arm/x86_32 platforms was dropped. - CFLAGS was change from -fsanitize=address with different --params to -fsanitize=kernel-address - If compiler doesn't support -fsanitize=kernel-address warning printed and build continues without -fsanitize - Removed kasan_memset/kasan_memcpy/kasan_memmove hooks. It turned out that this hooks are not needed. Compiler already instrument memset/memcpy/memmove (inserts __asan_load/__asan_store call before mem*() calls). - branch profiling disabled for mm/kasan/kasan.c to avoid recursion (__asan_load -> ftrace_likely_update -> __asan_load -> ...) - kasan hooks for buddy allocator moved to right places Comparison with other debuggin features: ======================================= KMEMCHECK: - KASan can do almost everything that kmemcheck can. KASan uses compile-time instrumentation, which makes it significantly faster than kmemcheck. The only advantage of kmemcheck over KASan is detection of unitialized memory reads. DEBUG_PAGEALLOC: - KASan is slower than DEBUG_PAGEALLOC, but KASan works on sub-page granularity level, so it able to find more bugs. SLUB_DEBUG (poisoning, redzones): - SLUB_DEBUG has lower overhead than KASan. - SLUB_DEBUG in most cases are not able to detect bad reads, KASan able to detect both reads and writes. - In some cases (e.g. redzone overwritten) SLUB_DEBUG detect bugs only on allocation/freeing of object. KASan catch bugs right before it will happen, so we always know exact place of first bad read/write. Basic idea: =========== The main idea of KASAN is to use shadow memory to record whether each byte of memory is safe to access or not, and use compiler's instrumentation to check the shadow memory on each memory access. Address sanitizer uses 1/8 of the memory addressable in kernel for shadow memory (on x86_64 16TB of virtual address space reserved for shadow to cover all 128TB) and uses direct mapping with a scale and offset to translate a memory address to its corresponding shadow address. Here is function to translate address to corresponding shadow address: unsigned long kasan_mem_to_shadow(unsigned long addr) { return (addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET; } where KASAN_SHADOW_SCALE_SHIFT = 3. So for every 8 bytes there is one corresponding byte of shadow memory. The following encoding used for each shadow byte: 0 means that all 8 bytes of the corresponding memory region are valid for access; k (1 <= k <= 7) means that the first k bytes are valid for access, and other (8 - k) bytes are not; Any negative value indicates that the entire 8-bytes are inaccessible. Different negative values used to distinguish between different kinds of inaccessible memory (redzones, freed memory) (see mm/kasan/kasan.h). To be able to detect accesses to bad memory we need a special compiler. Such compiler inserts a specific function calls (__asan_load*(addr), __asan_store*(addr)) before each memory access of size 1, 2, 4, 8 or 16. These functions check whether memory region is valid to access or not by checking corresponding shadow memory. If access is not valid an error printed. Andrey Ryabinin (13): Add kernel address sanitizer infrastructure. efi: libstub: disable KASAN for efistub x86_64: load_percpu_segment: read irq_stack_union.gs_base before load_segment x86_64: add KASan support mm: page_alloc: add kasan hooks on alloc and free paths mm: slub: introduce virt_to_obj function. mm: slub: share slab_err and object_err functions mm: slub: introduce metadata_access_enable()/metadata_access_disable() mm: slub: add kernel address sanitizer support for slub allocator fs: dcache: manually unpoison dname after allocation to shut up kasan's reports kmemleak: disable kasan instrumentation for kmemleak lib: add kasan test module kasan: introduce inline instrumentation Documentation/kasan.txt | 179 ++++++++++++++ Makefile | 16 +- arch/x86/Kconfig | 1 + arch/x86/boot/Makefile | 2 + arch/x86/boot/compressed/Makefile | 2 + arch/x86/include/asm/kasan.h | 27 +++ arch/x86/kernel/Makefile | 2 + arch/x86/kernel/cpu/common.c | 4 +- arch/x86/kernel/dumpstack.c | 5 +- arch/x86/kernel/head64.c | 9 +- arch/x86/kernel/head_64.S | 28 +++ arch/x86/mm/Makefile | 3 + arch/x86/mm/init.c | 3 + arch/x86/mm/kasan_init_64.c | 87 +++++++ arch/x86/realmode/Makefile | 2 +- arch/x86/realmode/rm/Makefile | 1 + arch/x86/vdso/Makefile | 1 + drivers/firmware/efi/libstub/Makefile | 1 + fs/dcache.c | 5 + include/linux/kasan.h | 72 ++++++ include/linux/sched.h | 3 + include/linux/slab.h | 11 +- include/linux/slub_def.h | 9 + lib/Kconfig.debug | 2 + lib/Kconfig.kasan | 54 +++++ lib/Makefile | 1 + lib/test_kasan.c | 254 ++++++++++++++++++++ mm/Makefile | 4 + mm/compaction.c | 2 + mm/kasan/Makefile | 3 + mm/kasan/kasan.c | 441 ++++++++++++++++++++++++++++++++++ mm/kasan/kasan.h | 37 +++ mm/kasan/report.c | 259 ++++++++++++++++++++ mm/kmemleak.c | 6 + mm/page_alloc.c | 3 + mm/slab_common.c | 5 +- mm/slub.c | 56 ++++- scripts/Makefile.lib | 10 + 38 files changed, 1595 insertions(+), 15 deletions(-) create mode 100644 Documentation/kasan.txt create mode 100644 arch/x86/include/asm/kasan.h create mode 100644 arch/x86/mm/kasan_init_64.c create mode 100644 include/linux/kasan.h create mode 100644 lib/Kconfig.kasan create mode 100644 lib/test_kasan.c create mode 100644 mm/kasan/Makefile create mode 100644 mm/kasan/kasan.c create mode 100644 mm/kasan/kasan.h create mode 100644 mm/kasan/report.c Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Konstantin Serebryany <kcc@xxxxxxxxxx> Cc: Dmitry Chernenkov <dmitryc@xxxxxxxxxx> Cc: Andrey Konovalov <adech.fo@xxxxxxxxx> Cc: Yuri Gribov <tetra2005@xxxxxxxxx> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx> Cc: Sasha Levin <sasha.levin@xxxxxxxxxx> Cc: Michal Marek <mmarek@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Andi Kleen <andi@xxxxxxxxxxxxxx> Cc: Vegard Nossum <vegard.nossum@xxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: <linux-kbuild@xxxxxxxxxxxxxxx> Cc: <x86@xxxxxxxxxx> Cc: <linux-mm@xxxxxxxxx> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Cc: Michal Marek <mmarek@xxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Dave Jones <davej@xxxxxxxxxx> -- 2.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
