Subject: [PATCH v2 6/9] powerpc/64s/hash: SLB fix preemption issues

From: Nicholas Piggin <[email-masked]>
Date: Wed, 3 Oct 2018 00:27:56 +1000

slb_setup_new_exec and preload_new_slb_context run with interrupts
and preemption enabled, which can be corrupted by re-entrant interrupt
or process touching SLB preload cache or SLB allocator.

Hard disable interrupts over these regions.

Fixes: 5e46e29e6a97 ("powerpc/64s/hash: convert SLB miss handlers to C")
Fixes: 89ca4e126a3f ("powerpc/64s/hash: Add a SLB preload cache")
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/mm/slb.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 8c38659f1b6b..b5a33da875b5 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -311,6 +311,8 @@ void slb_setup_new_exec(void)
 	struct mm_struct *mm = current->mm;
 	unsigned long exec = 0x10000000;
 
+	WARN_ON(irqs_disabled());
+
 	/*
 	 * preload cache can only be used to determine whether a SLB
 	 * entry exists if it does not start to overflow.
@@ -318,6 +320,8 @@ void slb_setup_new_exec(void)
 	if (ti->slb_preload_nr + 2 > SLB_PRELOAD_NR)
 		return;
 
+	hard_irq_disable();
+
 	/*
 	 * We have no good place to clear the slb preload cache on exec,
 	 * flush_thread is about the earliest arch hook but that happens
@@ -347,6 +351,8 @@ void slb_setup_new_exec(void)
 
 	/* see switch_slb */
 	asm volatile("isync" : : : "memory");
+
+	local_irq_enable();
 }
 
 void preload_new_slb_context(unsigned long start, unsigned long sp)
@@ -355,10 +361,14 @@ void preload_new_slb_context(unsigned long start, unsigned long sp)
 	struct mm_struct *mm = current->mm;
 	unsigned long heap = mm->start_brk;
 
+	WARN_ON(irqs_disabled());
+
 	/* see above */
 	if (ti->slb_preload_nr + 3 > SLB_PRELOAD_NR)
 		return;
 
+	hard_irq_disable();
+
 	/* Userspace entry address. */
 	if (!is_kernel_addr(start)) {
 		if (preload_add(ti, start))
@@ -379,6 +389,8 @@ void preload_new_slb_context(unsigned long start, unsigned long sp)
 
 	/* see switch_slb */
 	asm volatile("isync" : : : "memory");
+
+	local_irq_enable();
 }

-- 
2.18.0