From mboxrd@z Thu Jan 1 00:00:00 1970 From: kpark3469@gmail.com Date: Sun, 5 Feb 2017 16:14:09 +0400 Message-Id: <1486296850-16045-2-git-send-email-kpark3469@gmail.com> In-Reply-To: <1486296850-16045-1-git-send-email-kpark3469@gmail.com> References: <1486296850-16045-1-git-send-email-kpark3469@gmail.com> Subject: [kernel-hardening] [PATCH v3 2/3] arm64: usercopy: Implement stack frame object validation To: kernel-hardening@lists.openwall.com Cc: catalin.marinas@arm.com, keescook@chromium.org, will.deacon@arm.com, mark.rutland@arm.com, james.morse@arm.com, panand@redhat.com, keun-o.park@darkmatter.ae List-ID: From: Sahara This implements arch_within_stack_frames() for arm64 that should validate if a given object is contained by a kernel stack frame. Signed-off-by: Sahara Reviewed-by: James Morse --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/thread_info.h | 64 ++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1117421..8bf70b4 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -97,6 +97,7 @@ config ARM64 select HAVE_SYSCALL_TRACEPOINTS select HAVE_KPROBES select HAVE_KRETPROBES if HAVE_KPROBES + select HAVE_ARCH_WITHIN_STACK_FRAMES select IOMMU_DMA if IOMMU_SUPPORT select IRQ_DOMAIN select IRQ_FORCED_THREADING diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 46c3b93..70baad3 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -68,7 +68,71 @@ struct thread_info { #define thread_saved_fp(tsk) \ ((unsigned long)(tsk->thread.cpu_context.fp)) +#define get_stack_start(fp) (fp + 2 * sizeof(void *)) + +/* + * Walks up the stack frames to make sure that the specified object is + * entirely contained by a single stack frame. + * + * Returns: + * GOOD_FRAME if within a frame + * BAD_STACK if placed across a frame boundary (or outside stack) + * NOT_STACK unable to determine (no frame pointers, etc) + */ + +static inline enum stack_type arch_within_stack_frames(const void * const stack, + const void * const stackend, + const void *obj, unsigned long len) +{ +#ifdef CONFIG_FRAME_POINTER + const void *callee_fp = NULL; + const void *caller_fp = NULL; + + callee_fp = __builtin_frame_address(1); + if (callee_fp) + caller_fp = *(const void * const *)callee_fp; + /* + * Case #1: + * low ----------------------------------------------> high + * [callee_fp][lr][args][local vars][caller_fp'][lr'] + * ^----------------^ + * allow copies only within here + * + * Case #2: + * low ----------------------------------------------> high + * [check_object_size_fp][lr][args][local vars][callee_fp][lr] + * ^----------------^ + * dynamically allocated stack variable of + * callee frame copies are allowed within here + * + * < example code snippet for Case#2 > + * array_size = get_random_int() & 0x0f; + * if (to_user) { + * unsigned char array[array_size]; + * if (copy_to_user((void __user *)user_addr, array, + * unconst + sizeof(array))) { + */ + while (stack <= callee_fp && callee_fp < stackend && + !((unsigned long)caller_fp & 0xf)) { + /* + * If obj + len extends past the caller frame, this + * check won't pass and the next frame will be 0, + * causing us to bail out and correctly report + * the copy as invalid. + */ + if (!caller_fp || (obj + len <= caller_fp)) + return (obj >= get_stack_start(callee_fp)) ? + GOOD_FRAME : BAD_STACK; + callee_fp = caller_fp; + caller_fp = *(const void * const *)caller_fp; + } + return BAD_STACK; +#else + return NOT_STACK; #endif +} + +#endif /* !__ASSEMBLY__ */ /* * thread information flags: -- 2.7.4