[PATCH 5.14 062/151] x86/fpu: Mask out the invalid MXCSR bits properly

[Greg Kroah-Hartman]

From: Borislav Petkov <bp@xxxxxxx>

commit b2381acd3fd9bacd2c63f53b2c610c89959b31cc upstream.

This is a fix for the fix (yeah, /facepalm).

The correct mask to use is not the negation of the MXCSR_MASK but the
actual mask which contains the supported bits in the MXCSR register.

Reported and debugged by Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>

Fixes: d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits")
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Tested-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Tested-by: Ser Olmy <ser.olmy@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/YWgYIYXLriayyezv@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/kernel/fpu/signal.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -385,7 +385,7 @@ static int __fpu_restore_sig(void __user
 				return -EINVAL;
 		} else {
 			/* Mask invalid bits out for historical reasons (broken hardware). */
-			fpu->state.fxsave.mxcsr &= ~mxcsr_feature_mask;
+			fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
 		}
 
 		/* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */