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>

1 files changed, 9 insertions, 2 deletions

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 8aa96cbb5dfb..9e231d88bb33 100644
--- 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;