x86: fix fpu restore from sig return

If the task never used fpu, initialize the fpu before restoring the FP
state from the signal handler context. This will allocate the fpu
state, if the task never needed it before.

Reported-and-bisected-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Eric Sesterhenn <snakebyte@gmx.de>
Cc: Frederik Deweerdt <deweerdt@free.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 1 deletions

diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h
index da2adb45f6e3..6b722d315936 100644
--- a/include/asm-x86/i387.h
+++ b/include/asm-x86/i387.h
@@ -175,7 +175,15 @@ static inline int save_i387(struct _fpstate __user *buf)
  */
 static inline int restore_i387(struct _fpstate __user *buf)
 {
-        set_used_math();
+        struct task_struct *tsk = current;
+        int err;
+
+        if (!used_math()) {
+                err = init_fpu(tsk);
+                if (err)
+                        return err;
+        }
+
         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
                 clts();
                 task_thread_info(current)->status |= TS_USEDFPU;