[MIPS] Fix check for valid stack pointer during backtrace

The newly added check for valid stack pointer address breaks at least for
64bit kernels.  Use __get_user() for accessing stack content to avoid crashes,
when doing the backtrace.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 9 insertions, 7 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index cb8b0e2c7954..f9165d1a17bf 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -88,15 +88,17 @@ static void show_raw_backtrace(unsigned long reg29)
 #ifdef CONFIG_KALLSYMS
         printk("\n");
 #endif
-#define IS_KVA01(a) ((((unsigned int)a) & 0xc0000000) == 0x80000000)
-        if (IS_KVA01(sp)) {
-                while (!kstack_end(sp)) {
-                        addr = *sp++;
-                        if (__kernel_text_address(addr))
-                                print_ip_sym(addr);
+        while (!kstack_end(sp)) {
+                unsigned long __user *p =
+                        (unsigned long __user *)(unsigned long)sp++;
+                if (__get_user(addr, p)) {
+                        printk(" (Bad stack address)");
+                        break;
                 }
-                printk("\n");
+                if (__kernel_text_address(addr))
+                        print_ip_sym(addr);
         }
+        printk("\n");
 }
 
 #ifdef CONFIG_KALLSYMS