arm64: Change the on_*stack functions to take a size argument

unwind_frame() was previously implicitly checking that the frame
record is in bounds of the stack by enforcing that FP is both aligned
to 16 and in bounds of the stack. Once the FP alignment requirement
is relaxed to 8 this will not be sufficient because it does not
account for the case where FP points to 8 bytes before the end of the
stack.

Make the check explicit by changing the on_*stack functions to take a
size argument and adjusting the callers to pass the appropriate sizes.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ib7a3eb3eea41b0687ffaba045ceb2012d077d8b4
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210526174927.2477847-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>

6 files changed, 37 insertions, 34 deletions

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 9df3feeee890..7a094aafec20 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -329,13 +329,13 @@ long get_tagged_addr_ctrl(struct task_struct *task);
  * of header definitions for the use of task_stack_page.
  */
 
-#define current_top_of_stack()							\
-({										\
-	struct stack_info _info;						\
-	BUG_ON(!on_accessible_stack(current, current_stack_pointer, &_info));	\
-	_info.high;								\
+#define current_top_of_stack()								\
+({											\
+	struct stack_info _info;							\
+	BUG_ON(!on_accessible_stack(current, current_stack_pointer, 1, &_info));	\
+	_info.high;									\
 })
-#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, NULL))
+#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1, NULL))
 
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_PROCESSOR_H */
diff --git a/arch/arm64/include/asm/sdei.h b/arch/arm64/include/asm/sdei.h
index 63e0b92a5fbb..8bc30a5c4569 100644
--- a/arch/arm64/include/asm/sdei.h
+++ b/arch/arm64/include/asm/sdei.h
@@ -42,8 +42,9 @@ unsigned long sdei_arch_get_entry_point(int conduit);
 
 struct stack_info;
 
-bool _on_sdei_stack(unsigned long sp, struct stack_info *info);
-static inline bool on_sdei_stack(unsigned long sp,
+bool _on_sdei_stack(unsigned long sp, unsigned long size,
+		    struct stack_info *info);
+static inline bool on_sdei_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
@@ -51,7 +52,7 @@ static inline bool on_sdei_stack(unsigned long sp,
 	if (!IS_ENABLED(CONFIG_ARM_SDE_INTERFACE))
 		return false;
 	if (in_nmi())
-		return _on_sdei_stack(sp, info);
+		return _on_sdei_stack(sp, size, info);
 
 	return false;
 }
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 4b33ca620679..1801399204d7 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -69,14 +69,14 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 
 DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
 
-static inline bool on_stack(unsigned long sp, unsigned long low,
-				unsigned long high, enum stack_type type,
-				struct stack_info *info)
+static inline bool on_stack(unsigned long sp, unsigned long size,
+			    unsigned long low, unsigned long high,
+			    enum stack_type type, struct stack_info *info)
 {
 	if (!low)
 		return false;
 
-	if (sp < low || sp >= high)
+	if (sp < low || sp + size < sp || sp + size > high)
 		return false;
 
 	if (info) {
@@ -87,38 +87,38 @@ static inline bool on_stack(unsigned long sp, unsigned long low,
 	return true;
 }
 
-static inline bool on_irq_stack(unsigned long sp,
+static inline bool on_irq_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
 	unsigned long high = low + IRQ_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_IRQ, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_IRQ, info);
 }
 
 static inline bool on_task_stack(const struct task_struct *tsk,
-				 unsigned long sp,
+				 unsigned long sp, unsigned long size,
 				 struct stack_info *info)
 {
 	unsigned long low = (unsigned long)task_stack_page(tsk);
 	unsigned long high = low + THREAD_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_TASK, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_TASK, info);
 }
 
 #ifdef CONFIG_VMAP_STACK
 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
 
-static inline bool on_overflow_stack(unsigned long sp,
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 				struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_ptr(overflow_stack);
 	unsigned long high = low + OVERFLOW_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_OVERFLOW, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
 }
 #else
-static inline bool on_overflow_stack(unsigned long sp,
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
 			struct stack_info *info) { return false; }
 #endif
 
@@ -128,21 +128,21 @@ static inline bool on_overflow_stack(unsigned long sp,
  * context.
  */
 static inline bool on_accessible_stack(const struct task_struct *tsk,
-				       unsigned long sp,
+				       unsigned long sp, unsigned long size,
 				       struct stack_info *info)
 {
 	if (info)
 		info->type = STACK_TYPE_UNKNOWN;
 
-	if (on_task_stack(tsk, sp, info))
+	if (on_task_stack(tsk, sp, size, info))
 		return true;
 	if (tsk != current || preemptible())
 		return false;
-	if (on_irq_stack(sp, info))
+	if (on_irq_stack(sp, size, info))
 		return true;
-	if (on_overflow_stack(sp, info))
+	if (on_overflow_stack(sp, size, info))
 		return true;
-	if (on_sdei_stack(sp, info))
+	if (on_sdei_stack(sp, size, info))
 		return true;
 
 	return false;
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index eb2f73939b7b..499b6b2f9757 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -122,7 +122,7 @@ static bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
 {
 	return ((addr & ~(THREAD_SIZE - 1))  ==
 		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))) ||
-		on_irq_stack(addr, NULL);
+		on_irq_stack(addr, sizeof(unsigned long), NULL);
 }
 
 /**
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index 2c7ca449dd51..c524f96f97c4 100644
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -162,31 +162,33 @@ static int init_sdei_scs(void)
 	return err;
 }
 
-static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info)
+static bool on_sdei_normal_stack(unsigned long sp, unsigned long size,
+				 struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_NORMAL, info);
 }
 
-static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info)
+static bool on_sdei_critical_stack(unsigned long sp, unsigned long size,
+				   struct stack_info *info)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
 	unsigned long high = low + SDEI_STACK_SIZE;
 
-	return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info);
+	return on_stack(sp, size, low, high, STACK_TYPE_SDEI_CRITICAL, info);
 }
 
-bool _on_sdei_stack(unsigned long sp, struct stack_info *info)
+bool _on_sdei_stack(unsigned long sp, unsigned long size, struct stack_info *info)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return false;
 
-	if (on_sdei_critical_stack(sp, info))
+	if (on_sdei_critical_stack(sp, size, info))
 		return true;
 
-	if (on_sdei_normal_stack(sp, info))
+	if (on_sdei_normal_stack(sp, size, info))
 		return true;
 
 	return false;
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 36cf05d5eb9e..5c70f247645b 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -78,7 +78,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	if (fp & 0xf)
 		return -EINVAL;
 
-	if (!on_accessible_stack(tsk, fp, &info))
+	if (!on_accessible_stack(tsk, fp, 16, &info))
 		return -EINVAL;
 
 	if (test_bit(info.type, frame->stacks_done))