From 0cecca9d03c964abbd2b7927d0670eb70db4ebf2 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Wed, 3 Apr 2019 18:41:44 +0200 Subject: x86/fpu: Eager switch PKRU state MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit While most of a task's FPU state is only needed in user space, the protection keys need to be in place immediately after a context switch. The reason is that any access to userspace memory while running in kernel mode also needs to abide by the memory permissions specified in the protection keys. The "eager switch" is a preparation for loading the FPU state on return to userland. Instead of decoupling PKRU state from xstate, update PKRU within xstate on write operations by the kernel. For user tasks the PKRU should be always read from the xsave area and it should not change anything because the PKRU value was loaded as part of FPU restore. For kernel threads the default "init_pkru_value" will be written. Before this commit, the kernel thread would end up with a random value which it inherited from the previous user task. [ bigeasy: save pkru to xstate, no cache, don't use __raw_xsave_addr() ] [ bp: update commit message, sort headers properly in asm/fpu/xstate.h ] Signed-off-by: Rik van Riel Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Borislav Petkov Reviewed-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andi Kleen Cc: Andy Lutomirski Cc: Aubrey Li Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jann Horn Cc: "Jason A. Donenfeld" Cc: Joerg Roedel Cc: Juergen Gross Cc: "Kirill A. Shutemov" Cc: kvm ML Cc: Michal Hocko Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Radim Krčmář Cc: x86-ml Link: https://lkml.kernel.org/r/20190403164156.19645-16-bigeasy@linutronix.de --- arch/x86/mm/pkeys.c | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/x86/mm/pkeys.c') diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c index 50f65fc1b9a3..2ecbf4155f98 100644 --- a/arch/x86/mm/pkeys.c +++ b/arch/x86/mm/pkeys.c @@ -126,7 +126,6 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey * in the process's lifetime will not accidentally get access * to data which is pkey-protected later on. */ -static u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) | PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) | PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) | -- cgit v1.2.3