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Message-Id: <1485351983-13873-1-git-send-email-kpark3469@gmail.com>
Date: Wed, 25 Jan 2017 17:46:23 +0400
From: kpark3469@...il.com
To: kernel-hardening@...ts.openwall.com
Cc: catalin.marinas@....com,
keescook@...omium.org,
will.deacon@....com,
mark.rutland@....com,
james.morse@....com,
panand@...hat.com,
keun-o.park@...kmatter.ae
Subject: [PATCH] arm64: usercopy: Implement stack frame object validation
From: Sahara <keun-o.park@...kmatter.ae>
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 <keun-o.park@...kmatter.ae>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/thread_info.h | 55 ++++++++++++++++++++++++++++++++++++
2 files changed, 56 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..f610c44 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -68,7 +68,62 @@ struct thread_info {
#define thread_saved_fp(tsk) \
((unsigned long)(tsk->thread.cpu_context.fp))
+/*
+ * Walks up the stack frames to make sure that the specified object is
+ * entirely contained by a single stack frame.
+ *
+ * Returns:
+ * 1 if within a frame
+ * -1 if placed across a frame boundary (or outside stack)
+ * 0 unable to determine (no frame pointers, etc)
+ */
+static inline int arch_within_stack_frames(const void * const stack,
+ const void * const stackend,
+ const void *obj, unsigned long len)
+{
+#if defined(CONFIG_FRAME_POINTER)
+ const void *oldframe;
+ const void *callee_fp = NULL;
+ const void *caller_fp = NULL;
+
+ oldframe = __builtin_frame_address(1);
+ if (oldframe) {
+ callee_fp = __builtin_frame_address(2);
+ if (callee_fp)
+ caller_fp = __builtin_frame_address(3);
+ }
+ /*
+ * low ----------------------------------------------> high
+ * [callee_fp][lr][args][local vars][caller_fp'][lr']
+ * ^----------------^
+ * allow copies only within here
+ */
+ while (stack <= callee_fp && callee_fp < stackend) {
+ /*
+ * 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) {
+ if (obj + len <= stackend)
+ return (obj >= callee_fp + 2 * sizeof(void *)) ?
+ 1 : -1;
+ else
+ return -1;
+ }
+ if (obj + len <= caller_fp)
+ return (obj >= callee_fp + 2 * sizeof(void *)) ? 1 : -1;
+ callee_fp = caller_fp;
+ caller_fp = *(const void * const *)caller_fp;
+ }
+ return -1;
+#else
+ return 0;
#endif
+}
+
+#endif /* !__ASSEMBLY__ */
/*
* thread information flags:
--
2.7.4
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