x86/fpu/xstate: Fix __fpu_restore_sig() for XSAVES

When the kernel is using XSAVES compacted format, we cannot do
__copy_from_user() from a signal frame, which has standard-format data.
Fix it by using copyin_to_xsaves(), which converts between formats and
filters out all supervisor states that we do not allow userspace to
write.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <h.peter.anvin@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V Shankar <ravi.v.shankar@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1468253937-40008-2-git-send-email-fenghua.yu@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 8aa96cbb5dfba7a8302217d46a40cff58d0330c5..9e231d88bb336e3585325c06e15bcd3842054ece 100644 (file)
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -323,8 +323,15 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
                 */
                fpu__drop(fpu);
 
-               if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
-                   __copy_from_user(&env, buf, sizeof(env))) {
+               if (using_compacted_format()) {
+                       err = copyin_to_xsaves(NULL, buf_fx,
+                                              &fpu->state.xsave);
+               } else {
+                       err = __copy_from_user(&fpu->state.xsave,
+                                              buf_fx, state_size);
+               }
+
+               if (err || __copy_from_user(&env, buf, sizeof(env))) {
                        fpstate_init(&fpu->state);
                        trace_x86_fpu_init_state(fpu);
                        err = -1;