x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing()

Now that user_xfeatures is correctly set when xsave is enabled, remove
the duplicated initialization of components.

Rename the function while at it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121457.377341297@linutronix.de

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d552410..a1a7013 100644 (file)
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -251,33 +251,27 @@ sanitize_restored_user_xstate(union fpregs_state *state,
 }
 
 /*
- * Restore the extended state if present. Otherwise, restore the FP/SSE state.
+ * Restore the FPU state directly from the userspace signal frame.
  */
-static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
+static int restore_fpregs_from_user(void __user *buf, u64 xrestore, bool fx_only)
 {
-       u64 init_bv;
-       int r;
-
        if (use_xsave()) {
-               if (fx_only) {
-                       init_bv = xfeatures_mask_uabi() & ~XFEATURE_MASK_FPSSE;
+               u64 init_bv = xfeatures_mask_uabi() & ~xrestore;
+               int ret;
 
-                       r = fxrstor_from_user_sigframe(buf);
-                       if (!r)
-                               os_xrstor(&init_fpstate.xsave, init_bv);
-                       return r;
-               } else {
-                       init_bv = xfeatures_mask_uabi() & ~xbv;
-
-                       r = xrstor_from_user_sigframe(buf, xbv);
-                       if (!r && unlikely(init_bv))
-                               os_xrstor(&init_fpstate.xsave, init_bv);
-                       return r;
-               }
+               if (likely(!fx_only))
+                       ret = xrstor_from_user_sigframe(buf, xrestore);
+               else
+                       ret = fxrstor_from_user_sigframe(buf);
+
+               if (!ret && unlikely(init_bv))
+                       os_xrstor(&init_fpstate.xsave, init_bv);
+               return ret;
        } else if (use_fxsr()) {
                return fxrstor_from_user_sigframe(buf);
-       } else
+       } else {
                return frstor_from_user_sigframe(buf);
+       }
 }
 
 static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
@@ -314,7 +308,7 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
                 */
                fpregs_lock();
                pagefault_disable();
-               ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
+               ret = restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only);
                pagefault_enable();
                if (!ret) {