[PATCH] x86: use probe_kernel_address in handle_BUG()

Avoid possible deadlock on a BUG() inside down_write(mmap_sem).  The deadlock
can only occur if something has gone horridly wrong, because a fault here
shouldn't happen.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 21aa1cd57773..a13037fe0ee3 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -28,6 +28,7 @@
 #include <linux/kprobes.h>
 #include <linux/kexec.h>
 #include <linux/unwind.h>
+#include <linux/uaccess.h>
 
 #ifdef CONFIG_EISA
 #include <linux/ioport.h>
@@ -40,7 +41,6 @@
 
 #include <asm/processor.h>
 #include <asm/system.h>
-#include <asm/uaccess.h>
 #include <asm/io.h>
 #include <asm/atomic.h>
 #include <asm/debugreg.h>
@@ -409,7 +409,7 @@ static void handle_BUG(struct pt_regs *regs)
 
         if (eip < PAGE_OFFSET)
                 return;
-        if (__get_user(ud2, (unsigned short __user *)eip))
+        if (probe_kernel_address((unsigned short __user *)eip, ud2))
                 return;
         if (ud2 != 0x0b0f)
                 return;
@@ -422,7 +422,8 @@ static void handle_BUG(struct pt_regs *regs)
                 char *file;
                 char c;
 
-                if (__get_user(line, (unsigned short __user *)(eip + 2)))
+                if (probe_kernel_address((unsigned short __user *)(eip + 2),
+                                        line))
                         break;
                 if (__get_user(file, (char * __user *)(eip + 4)) ||
                     (unsigned long)file < PAGE_OFFSET || __get_user(c, file))