From 3c1940c54922c2f5d434f11f568045dc5e5154f4 Mon Sep 17 00:00:00 2001 From: Kyle Huey Date: Mon, 9 Jan 2023 13:02:13 -0800 Subject: [PATCH] x86/fpu: Emulate XRSTOR's behavior if the xfeatures PKRU bit is not set commit d7e5aceace514a2b1b3ca3dc44f93f1704766ca7 upstream The hardware XRSTOR instruction resets the PKRU register to its hardware init value (namely 0) if the PKRU bit is not set in the xfeatures mask. Emulating that here restores the pre-5.14 behavior for PTRACE_SET_REGSET with NT_X86_XSTATE, and makes sigreturn (which still uses XRSTOR) and behave identically. Fixes: e84ba47e313d ("x86/fpu: Hook up PKRU into ptrace()") Signed-off-by: Kyle Huey Signed-off-by: Dave Hansen Link: https://lore.kernel.org/all/20221115230932.7126-6-khuey%40kylehuey.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/fpu/xstate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index fe9050c60adc3..8bbf37c0bebe2 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1168,7 +1168,8 @@ static int copy_uabi_to_xstate(struct xregs_state *xsave, const void *kbuf, xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU); *pkru = xpkru->pkru; - } + } else + *pkru = 0; /* * The state that came in from userspace was user-state only. -- 2.30.2