2 files changed, 19 insertions, 3 deletions

diff --git a/arch/um/kernel/trap_kern.c b/arch/um/kernel/trap_kern.c
index 87cc6fd76ced..90690b9b1f30 100644
--- a/arch/um/kernel/trap_kern.c
+++ b/arch/um/kernel/trap_kern.c
@@ -18,6 +18,7 @@
 #include "asm/a.out.h"
 #include "asm/current.h"
 #include "asm/irq.h"
+#include "sysdep/sigcontext.h"
 #include "user_util.h"
 #include "kern_util.h"
 #include "kern.h"
@@ -125,7 +126,15 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
         }
         else if(current->mm == NULL)
                 panic("Segfault with no mm");
-        err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
+
+        if (SEGV_IS_FIXABLE(&fi))
+                err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
+        else {
+                err = -EFAULT;
+                /* A thread accessed NULL, we get a fault, but CR2 is invalid.
+                 * This code is used in __do_copy_from_user() of TT mode. */
+                address = 0;
+        }
 
         catcher = current->thread.fault_catcher;
         if(!err)
diff --git a/arch/um/kernel/tt/uaccess_user.c b/arch/um/kernel/tt/uaccess_user.c
index f01475512ecb..8c220f054b61 100644
--- a/arch/um/kernel/tt/uaccess_user.c
+++ b/arch/um/kernel/tt/uaccess_user.c
@@ -22,8 +22,15 @@ int __do_copy_from_user(void *to, const void *from, int n,
                                __do_copy, &faulted);
         TASK_REGS(get_current())->tt = save;
 
-        if(!faulted) return(0);
-        else return(n - (fault - (unsigned long) from));
+        if(!faulted)
+                return 0;
+        else if (fault)
+                return n - (fault - (unsigned long) from);
+        else
+                /* In case of a general protection fault, we don't have the
+                 * fault address, so NULL is used instead. Pretend we didn't
+                 * copy anything. */
+                return n;
 }
 
 static void __do_strncpy(void *dst, const void *src, int count)