[PATCH] unicore32: check stack pointer in get_wchan

[Young Xiao <92siuyang@gmail.com>]

get_wchan() is lockless. Task may wakeup at any time and change its own 
stack, thus each next stack frame may be overwritten and filled with 
random stuff.

This patch fixes oops in unwind_frame() by adding stack pointer validation
on each step (as x86 code do), unwind_frame() already checks frame pointer.

See commit 1b15ec7a7427 ("ARM: 7912/1: check stack pointer in get_wchan")
for details.

Signed-off-by: Young Xiao <92siuyang@gmail.com>
---
 arch/unicore32/kernel/process.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/unicore32/kernel/process.c b/arch/unicore32/kernel/process.c
index 2bc10b8..1899ebc 100644
--- a/arch/unicore32/kernel/process.c
+++ b/arch/unicore32/kernel/process.c
@@ -277,6 +277,7 @@ EXPORT_SYMBOL(dump_fpu);
 unsigned long get_wchan(struct task_struct *p)
 {
 	struct stackframe frame;
+	unsigned long stack_page;
 	int count = 0;
 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;
@@ -285,9 +286,11 @@ unsigned long get_wchan(struct task_struct *p)
 	frame.sp = thread_saved_sp(p);
 	frame.lr = 0;			/* recovered from the stack */
 	frame.pc = thread_saved_pc(p);
+	stack_page = (unsigned long)task_stack_page(p);
 	do {
-		int ret = unwind_frame(&frame);
-		if (ret < 0)
+		if (frame.sp < stack_page ||
+		    frame.sp >= stack_page + THREAD_SIZE ||
+		    unwind_frame(&frame) < 0)
 			return 0;
 		if (!in_sched_functions(frame.pc))
 			return frame.pc;
-- 
2.7.4