From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 990784b57731192b7d90c8d4049e6318d81e887d ]
When PTI is disabled at boot time either because the CPU is not affected or PTI has been disabled on the command line, the boot code still calls into pti_finalize() which then unconditionally invokes:
pti_clone_entry_text() pti_clone_kernel_text()
pti_clone_kernel_text() was called unconditionally before the 32bit support was added and 32bit added the call to pti_clone_entry_text().
The call has no side effects as cloning the page tables into the available second one, which was allocated for PTI does not create damage. But it does not make sense either and in case that this functionality would be extended later this might actually lead to hard to diagnose issues.
Neither function should be called when PTI is runtime disabled. Make the invocation conditional.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Dave Hansen dave.hansen@linux.intel.com Acked-by: Ingo Molnar mingo@kernel.org Acked-by: Song Liu songliubraving@fb.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20190828143124.063353972@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/mm/pti.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 4df3e5c89d57c..c1ba376484a5b 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -643,6 +643,8 @@ void __init pti_init(void) */ void pti_finalize(void) { + if (!boot_cpu_has(X86_FEATURE_PTI)) + return; /* * We need to clone everything (again) that maps parts of the * kernel image.