[PATCH v4 0/3] usercopy: reimplement arch_within_stack_frames

[PATCH v4 0/3] usercopy: reimplement arch_within_stack_frames

[kpark3469]

From: Sahara <keun-o.park@darkmatter.ae>

This series of patches introduce the arm64 arch_within_stack_frames
implementation using stacktrace functions. Also the base code is
moved from thread_info.h to stacktrace.h. x86 code is reimplemented
to use frame pointer unwinder functions.

Note: The code is still missing in case of using x86 ORC unwinder and
guess unwinder.

v2 changes:
 - Remove 'arm64: usercopy: consider dynamic array stack variable'
 - minor fix in x86 arch_within_stack_frames code.
v3 changes:
 - Fix build problem caused by circular inclusion of header in x86 UP config
v4 changes:
 - Fix build problem caused by page_ext.h change

James Morse (1):
  arm64: usercopy: implement arch_within_stack_frames

Sahara (2):
  stacktrace: move arch_within_stack_frames from thread_info.h
  x86: usercopy: reimplement arch_within_stack_frames with unwinder

 arch/arm64/Kconfig                 |  1 +
 arch/arm64/kernel/stacktrace.c     | 76 +++++++++++++++++++++++++++++++++
 arch/x86/include/asm/thread_info.h | 51 +---------------------
 arch/x86/include/asm/unwind.h      |  5 +++
 arch/x86/kernel/Makefile           |  2 +-
 arch/x86/kernel/stacktrace.c       | 87 ++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/unwind_frame.c     |  4 +-
 include/linux/stacktrace.h         | 24 +++++++++++
 include/linux/thread_info.h        | 21 ---------
 mm/usercopy.c                      |  2 +-
 10 files changed, 197 insertions(+), 76 deletions(-)

-- 
2.7.4

[PATCH v4 1/3] stacktrace: move arch_within_stack_frames from thread_info.h

[kpark3469]

From: Sahara <keun-o.park@darkmatter.ae>

Since the inlined arch_within_stack_frames function was placed within
asm/thread_info.h, using stacktrace functions to unwind stack was
restricted. Now in order to have this function use more abundant apis,
it is moved to architecture's stacktrace.c. And, it is changed from
inline to noinline function to clearly have three depth calls like:

do_usercopy_stack()
  copy_[to|from]_user() : inline
    check_copy_size() : inline
      __check_object_size()
        check_stack_object()
          arch_within_stack_frames()

With this change, the x86's implementation was slightly changed also.

Signed-off-by: Sahara <keun-o.park@darkmatter.ae>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/include/asm/thread_info.h | 51 +-------------------------------------
 arch/x86/kernel/Makefile           |  2 +-
 arch/x86/kernel/stacktrace.c       | 49 ++++++++++++++++++++++++++++++++++++
 include/linux/stacktrace.h         | 24 ++++++++++++++++++
 include/linux/thread_info.h        | 21 ----------------
 mm/usercopy.c                      |  2 +-
 6 files changed, 76 insertions(+), 73 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index a5d9521..e25d70a 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -156,59 +156,10 @@ struct thread_info {
  *
  * preempt_count needs to be 1 initially, until the scheduler is functional.
  */
-#ifndef __ASSEMBLY__
-
-/*
- * 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 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 *frame = NULL;
-	const void *oldframe;
-
-	oldframe = __builtin_frame_address(1);
-	if (oldframe)
-		frame = __builtin_frame_address(2);
-	/*
-	 * low ----------------------------------------------> high
-	 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
-	 *                     ^----------------^
-	 *               allow copies only within here
-	 */
-	while (stack <= frame && frame < stackend) {
-		/*
-		 * If obj + len extends past the last 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 (obj + len <= frame)
-			return obj >= oldframe + 2 * sizeof(void *) ?
-				GOOD_FRAME : BAD_STACK;
-		oldframe = frame;
-		frame = *(const void * const *)frame;
-	}
-	return BAD_STACK;
-#else
-	return NOT_STACK;
-#endif
-}
-
-#else /* !__ASSEMBLY__ */
-
+#ifdef __ASSEMBLY__
 #ifdef CONFIG_X86_64
 # define cpu_current_top_of_stack (cpu_tss_rw + TSS_sp1)
 #endif
-
 #endif
 
 #ifdef CONFIG_COMPAT
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 02d6f5c..3b8afd5 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -70,7 +70,7 @@ obj-$(CONFIG_IA32_EMULATION)	+= tls.o
 obj-y				+= step.o
 obj-$(CONFIG_INTEL_TXT)		+= tboot.o
 obj-$(CONFIG_ISA_DMA_API)	+= i8237.o
-obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
+obj-y				+= stacktrace.o
 obj-y				+= cpu/
 obj-y				+= acpi/
 obj-y				+= reboot.o
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 093f2ea..ff178a0 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -12,6 +12,54 @@
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
 
+
+/*
+ * 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)
+ */
+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 *frame = NULL;
+	const void *oldframe;
+
+	oldframe = __builtin_frame_address(2);
+	if (oldframe)
+		frame = __builtin_frame_address(3);
+	/*
+	 * low ----------------------------------------------> high
+	 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
+	 *                     ^----------------^
+	 *               allow copies only within here
+	 */
+	while (stack <= frame && frame < stackend) {
+		/*
+		 * If obj + len extends past the last 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 (obj + len <= frame)
+			return obj >= oldframe + 2 * sizeof(void *) ?
+				GOOD_FRAME : BAD_STACK;
+		oldframe = frame;
+		frame = *(const void * const *)frame;
+	}
+	return BAD_STACK;
+#else
+	return NOT_STACK;
+#endif
+}
+
+#ifdef CONFIG_STACKTRACE
+
 static int save_stack_address(struct stack_trace *trace, unsigned long addr,
 			      bool nosched)
 {
@@ -241,3 +289,4 @@ void save_stack_trace_user(struct stack_trace *trace)
 	if (trace->nr_entries < trace->max_entries)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
+#endif /* CONFIG_STACKTRACE */
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index ba29a06..60bb988 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -7,6 +7,30 @@
 struct task_struct;
 struct pt_regs;
 
+/*
+ * For per-arch arch_within_stack_frames() implementations, defined in
+ * kernel/stacktrace.c.
+ */
+enum {
+	BAD_STACK = -1,
+	NOT_STACK = 0,
+	GOOD_FRAME,
+	GOOD_STACK,
+};
+
+#ifdef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
+extern int arch_within_stack_frames(const void * const stack,
+				    const void * const stackend,
+				    const void *obj, unsigned long len);
+#else
+static inline int arch_within_stack_frames(const void * const stack,
+					   const void * const stackend,
+					   const void *obj, unsigned long len)
+{
+	return NOT_STACK;
+}
+#endif
+
 #ifdef CONFIG_STACKTRACE
 struct stack_trace {
 	unsigned int nr_entries, max_entries;
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 34f053a..5403851 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -23,18 +23,6 @@
 #endif
 
 #include <linux/bitops.h>
-
-/*
- * For per-arch arch_within_stack_frames() implementations, defined in
- * asm/thread_info.h.
- */
-enum {
-	BAD_STACK = -1,
-	NOT_STACK = 0,
-	GOOD_FRAME,
-	GOOD_STACK,
-};
-
 #include <asm/thread_info.h>
 
 #ifdef __KERNEL__
@@ -92,15 +80,6 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
 
 #define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
 
-#ifndef CONFIG_HAVE_ARCH_WITHIN_STACK_FRAMES
-static inline int arch_within_stack_frames(const void * const stack,
-					   const void * const stackend,
-					   const void *obj, unsigned long len)
-{
-	return 0;
-}
-#endif
-
 #ifdef CONFIG_HARDENED_USERCOPY
 extern void __check_object_size(const void *ptr, unsigned long n,
 					bool to_user);
diff --git a/mm/usercopy.c b/mm/usercopy.c
index e9e9325..6a74776 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -19,7 +19,7 @@
 #include <linux/sched.h>
 #include <linux/sched/task.h>
 #include <linux/sched/task_stack.h>
-#include <linux/thread_info.h>
+#include <linux/stacktrace.h>
 #include <asm/sections.h>
 
 /*
-- 
2.7.4

[PATCH v4 2/3] arm64: usercopy: implement arch_within_stack_frames

[kpark3469]

From: James Morse <james.morse@arm.com>

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: James Morse <james.morse@arm.com>
Reviewed-by: Sahara <keun-o.park@darkmatter.ae>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/Kconfig             |  1 +
 arch/arm64/kernel/stacktrace.c | 76 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index eb2cf49..4498ff4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -128,6 +128,7 @@ config ARM64
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
+	select HAVE_ARCH_WITHIN_STACK_FRAMES
 	select IOMMU_DMA if IOMMU_SUPPORT
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index d5718a0..5eb3784 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -27,6 +27,11 @@
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
 
+#define FAKE_FRAME(frame, my_func) do {				\
+	frame.fp = (unsigned long)__builtin_frame_address(0);	\
+	frame.pc = (unsigned long)my_func;			\
+} while (0)
+
 /*
  * AArch64 PCS assigns the frame pointer to x29.
  *
@@ -100,6 +105,77 @@ void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 	}
 }
 
+struct check_frame_arg {
+	unsigned long obj_start;
+	unsigned long obj_end;
+	unsigned long frame_start;
+	int discard_frames;
+	int err;
+};
+
+static int check_frame(struct stackframe *frame, void *d)
+{
+	struct check_frame_arg *arg = d;
+	unsigned long frame_end = frame->fp;
+
+	/* object overlaps multiple frames */
+	if (arg->obj_start < frame->fp && frame->fp < arg->obj_end) {
+		arg->err = BAD_STACK;
+		return 1;
+	}
+
+	/*
+	 * Discard frames and check object is in a frame written early
+	 * enough.
+	 */
+	if (arg->discard_frames)
+		arg->discard_frames--;
+	else if ((arg->frame_start <= arg->obj_start &&
+			arg->obj_start < frame_end) &&
+		(arg->frame_start < arg->obj_end && arg->obj_end <= frame_end))
+		return 1;
+
+	/* object exists in a previous frame */
+	if (arg->obj_end < arg->frame_start) {
+		arg->err = BAD_STACK;
+		return 1;
+	}
+
+	arg->frame_start = frame_end + 0x10;
+
+	return 0;
+}
+
+/* Check obj doesn't overlap a stack frame record */
+int arch_within_stack_frames(const void *stack,
+			     const void *stack_end,
+			     const void *obj, unsigned long obj_len)
+{
+	struct stackframe frame;
+	struct check_frame_arg arg;
+
+	if (!IS_ENABLED(CONFIG_FRAME_POINTER))
+		return NOT_STACK;
+
+	arg.err = GOOD_FRAME;
+	arg.obj_start = (unsigned long)obj;
+	arg.obj_end = arg.obj_start + obj_len;
+
+	FAKE_FRAME(frame, arch_within_stack_frames);
+	arg.frame_start = frame.fp;
+
+	/*
+	 * Skip 4 non-inlined frames: <fake frame>,
+	 * arch_within_stack_frames(), check_stack_object() and
+	 * __check_object_size().
+	 */
+	arg.discard_frames = 4;
+
+	walk_stackframe(current, &frame, check_frame, &arg);
+
+	return arg.err;
+}
+
 #ifdef CONFIG_STACKTRACE
 struct stack_trace_data {
 	struct stack_trace *trace;
-- 
2.7.4

[PATCH v4 3/3] x86: usercopy: reimplement arch_within_stack_frames with unwinder

[kpark3469]

From: Sahara <keun-o.park@darkmatter.ae>

The old arch_within_stack_frames which used the frame pointer is
now reimplemented to use frame pointer unwinder apis. So the main
functionality is same as before.

Signed-off-by: Sahara <keun-o.park@darkmatter.ae>
---
 arch/x86/include/asm/unwind.h  |  5 ++++
 arch/x86/kernel/stacktrace.c   | 64 +++++++++++++++++++++++++++++++++---------
 arch/x86/kernel/unwind_frame.c |  4 +--
 3 files changed, 57 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 1f86e1b..6f04906f 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -87,6 +87,11 @@ void unwind_init(void);
 void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
 			void *orc, size_t orc_size);
 #else
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+#define FRAME_HEADER_SIZE (sizeof(long) * 2)
+size_t regs_size(struct pt_regs *regs);
+#endif
+
 static inline void unwind_init(void) {}
 static inline
 void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index ff178a0..3de1105 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -13,6 +13,33 @@
 #include <asm/unwind.h>
 
 
+static inline void *get_cur_frame(struct unwind_state *state)
+{
+	void *frame = NULL;
+
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+	if (state->regs)
+		frame = (void *)state->regs;
+	else
+		frame = (void *)state->bp;
+#endif
+	return frame;
+}
+
+static inline void *get_frame_end(struct unwind_state *state)
+{
+	void *frame_end = NULL;
+
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+	if (state->regs) {
+		frame_end = (void *)state->regs + regs_size(state->regs);
+	} else {
+		frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
+	}
+#endif
+	return frame_end;
+}
+
 /*
  * Walks up the stack frames to make sure that the specified object is
  * entirely contained by a single stack frame.
@@ -26,31 +53,42 @@ 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 *frame = NULL;
-	const void *oldframe;
-
-	oldframe = __builtin_frame_address(2);
-	if (oldframe)
-		frame = __builtin_frame_address(3);
+#if defined(CONFIG_UNWINDER_FRAME_POINTER)
+	struct unwind_state state;
+	void *prev_frame_end = NULL;
 	/*
 	 * low ----------------------------------------------> high
 	 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
 	 *                     ^----------------^
 	 *               allow copies only within here
+	 *
+	 * Skip 3 non-inlined frames: arch_within_stack_frames(),
+	 * check_stack_object() and __check_object_size().
+	 *
 	 */
-	while (stack <= frame && frame < stackend) {
+	unsigned int discard_frames = 3;
+
+	for (unwind_start(&state, current, NULL, NULL); !unwind_done(&state);
+	     unwind_next_frame(&state)) {
 		/*
 		 * If obj + len extends past the last 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 (obj + len <= frame)
-			return obj >= oldframe + 2 * sizeof(void *) ?
-				GOOD_FRAME : BAD_STACK;
-		oldframe = frame;
-		frame = *(const void * const *)frame;
+		if (discard_frames) {
+			discard_frames--;
+		} else {
+			void *frame = get_cur_frame(&state);
+
+			if (!frame || !prev_frame_end)
+				return NOT_STACK;
+			if (obj + len <= frame)
+				return obj >= prev_frame_end ?
+						GOOD_FRAME : BAD_STACK;
+		}
+		/* save current frame end before move to next frame */
+		prev_frame_end = get_frame_end(&state);
 	}
 	return BAD_STACK;
 #else
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 3dc26f9..c8bfa5c 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -8,8 +8,6 @@
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
 
-#define FRAME_HEADER_SIZE (sizeof(long) * 2)
-
 unsigned long unwind_get_return_address(struct unwind_state *state)
 {
 	if (unwind_done(state))
@@ -69,7 +67,7 @@ static void unwind_dump(struct unwind_state *state)
 	}
 }
 
-static size_t regs_size(struct pt_regs *regs)
+size_t regs_size(struct pt_regs *regs)
 {
 	/* x86_32 regs from kernel mode are two words shorter: */
 	if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
-- 
2.7.4