x86/fpu/signal: Remove the legacy alignment check

Checking for the XSTATE buffer being 64-byte aligned, and if not,
deciding just to restore the FXSR state is daft.

If user space provides an unaligned math frame and has the extended state
magic set in the FX software reserved bytes, then it really can keep the
pieces.

If the frame is unaligned and the FX software magic is not set, then
fx_only is already set and the restore will use fxrstor.

Remove 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/20210623121457.184149902@linutronix.de

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 42e85c3..8a327c0 100644 (file)
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -306,9 +306,6 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
                }
        }
 
-       if ((unsigned long)buf_fx % 64)
-               fx_only = 1;
-
        if (!ia32_fxstate) {
                /*
                 * Attempt to restore the FPU registers directly from user