Subject: [PATCH 1/6] powerpc/64/kuap: move kuap checks out of MSR[RI]=0 regions of exit code

From: Nicholas Piggin <[email-masked]>
Date: Wed, 29 Apr 2020 16:26:01 +1000

Any kind of WARN causes a program check that will crash with
unrecoverable exception if it occurs when RI is clear.

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kernel/syscall_64.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 8f7e268f3294..a37c7717424f 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -35,6 +35,8 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	BUG_ON(!FULL_REGS(regs));
 	BUG_ON(regs->softe != IRQS_ENABLED);
 
+	kuap_check_amr();
+
 	account_cpu_user_entry();
 
 #ifdef CONFIG_PPC_SPLPAR
@@ -47,8 +49,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	}
 #endif
 
-	kuap_check_amr();
-
 	/*
 	 * This is not required for the syscall exit path, but makes the
 	 * stack frame look nicer. If this was initialised in the first stack
@@ -142,6 +142,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	unsigned long ti_flags;
 	unsigned long ret = 0;
 
+	kuap_check_amr();
+
 	regs->result = r3;
 
 	/* Check whether the syscall is issued inside a restartable sequence */
@@ -218,8 +220,6 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	local_paca->tm_scratch = regs->msr;
 #endif
 
-	kuap_check_amr();
-
 	account_cpu_user_exit();
 
 	return ret;
@@ -242,6 +242,8 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	BUG_ON(!FULL_REGS(regs));
 	BUG_ON(regs->softe != IRQS_ENABLED);
 
+	kuap_check_amr();
+
 	local_irq_save(flags);
 
 again:
@@ -298,8 +300,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	local_paca->tm_scratch = regs->msr;
 #endif
 
-	kuap_check_amr();
-
 	account_cpu_user_exit();
 
 	return ret;
@@ -319,6 +319,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 	BUG_ON(regs->msr & MSR_PR);
 	BUG_ON(!FULL_REGS(regs));
 
+	kuap_check_amr();
+
 	if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
 		clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
 		ret = 1;
-- 
2.23.0