[UPDATED PATCH] Fix check for valid stack pointer during backtrace

[UPDATED PATCH] Fix check for valid stack pointer during backtrace

[Thomas Bogendoerfer]

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>
---

 arch/mips/kernel/traps.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index cb8b0e2..f9165d1 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

Re: [UPDATED PATCH] Fix check for valid stack pointer during backtrace

[Ralf Baechle]

On Mon, May 12, 2008 at 05:58:48PM +0200, Thomas Bogendoerfer wrote:

> 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>

Applied.  Thanks,

  Ralf