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x86/fpu: Mask PKRU from kernel XRSTOR[S] operations

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As the PKRU state is managed separately restoring it from the xstate
buffer would be counterproductive as it might either restore a stale
value or reinit the PKRU state to 0.

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/20210623121456.606745195@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-06-23 14:02:20 +02:00 committed by Borislav Petkov
parent e84ba47e31
commit 30a304a138
4 changed files with 14 additions and 3 deletions
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4
arch/x86/include/asm/fpu/internal.h
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@ -259,7 +259,7 @@ static inline void fxsave(struct fxregs_state *fx)
*/
static inline void os_xrstor_booting(struct xregs_state *xstate)
{
u64 mask = -1;
u64 mask = xfeatures_mask_fpstate();
u32 lmask = mask;
u32 hmask = mask >> 32;
int err;
@ -388,7 +388,7 @@ extern void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
{
__restore_fpregs_from_fpstate(fpstate, -1);
__restore_fpregs_from_fpstate(fpstate, xfeatures_mask_fpstate());
}
extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);

10
arch/x86/include/asm/fpu/xstate.h
View File

@ -111,6 +111,16 @@ static inline u64 xfeatures_mask_restore_user(void)
return xfeatures_mask_all & XFEATURE_MASK_USER_RESTORE;
}
/*
* Like xfeatures_mask_restore_user() but additionally restors the
* supported supervisor states.
*/
static inline u64 xfeatures_mask_fpstate(void)
{
return xfeatures_mask_all & \
(XFEATURE_MASK_USER_RESTORE | XFEATURE_MASK_SUPERVISOR_SUPPORTED);
}
static inline u64 xfeatures_mask_independent(void)
{
if (!boot_cpu_has(X86_FEATURE_ARCH_LBR))

1
arch/x86/kernel/fpu/xstate.c
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@ -60,6 +60,7 @@ static short xsave_cpuid_features[] __initdata = {
* XSAVE buffer, both supervisor and user xstates.
*/
u64 xfeatures_mask_all __ro_after_init;
EXPORT_SYMBOL_GPL(xfeatures_mask_all);
static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
{ [ 0 ... XFEATURE_MAX - 1] = -1};

2
arch/x86/mm/extable.c
View File

@ -65,7 +65,7 @@ __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
(void *)instruction_pointer(regs));
__restore_fpregs_from_fpstate(&init_fpstate, -1);
__restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
return true;
}
EXPORT_SYMBOL_GPL(ex_handler_fprestore);