Pull kmalloc into release branch

[pandora-kernel.git] / arch / arm / mm / fault.c

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 0b6c4db..c5e0622 100644 (file)
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -8,7 +8,6 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#include <linux/config.h>
 #include <linux/module.h>
 #include <linux/signal.h>
 #include <linux/ptrace.h>
@@ -233,7 +232,17 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
        if (in_interrupt() || !mm)
                goto no_context;
 
-       down_read(&mm->mmap_sem);
+       /*
+        * As per x86, we may deadlock here.  However, since the kernel only
+        * validly references user space from well defined areas of the code,
+        * we can bug out early if this is from code which shouldn't.
+        */
+       if (!down_read_trylock(&mm->mmap_sem)) {
+               if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
+                       goto no_context;
+               down_read(&mm->mmap_sem);
+       }
+
        fault = __do_page_fault(mm, addr, fsr, tsk);
        up_read(&mm->mmap_sem);