linux-kernel - [PATCH 5.15 112/177] powerpc/85xx: Fix oops when CONFIG_FSL

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Date:   Mon, 20 Dec 2021 15:34:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Martin Kennedy <hurricos@...il.com>,
        Xiaoming Ni <nixiaoming@...wei.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 112/177] powerpc/85xx: Fix oops when CONFIG_FSL_PMC=n

From: Xiaoming Ni <nixiaoming@...wei.com>

[ Upstream commit 3dc709e518b47386e6af937eaec37bb36539edfd ]

When CONFIG_FSL_PMC is set to n, no value is assigned to cpu_up_prepare
in the mpc85xx_pm_ops structure. As a result, oops is triggered in
smp_85xx_start_cpu().

  smp: Bringing up secondary CPUs ...
  kernel tried to execute user page (0) - exploit attempt? (uid: 0)
  BUG: Unable to handle kernel instruction fetch (NULL pointer?)
  Faulting instruction address: 0x00000000
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP [00000000] 0x0
  LR [c0021d2c] smp_85xx_kick_cpu+0xe8/0x568
  Call Trace:
  [c1051da8] [c0021cb8] smp_85xx_kick_cpu+0x74/0x568 (unreliable)
  [c1051de8] [c0011460] __cpu_up+0xc0/0x228
  [c1051e18] [c0031bbc] bringup_cpu+0x30/0x224
  [c1051e48] [c0031f3c] cpu_up.constprop.0+0x180/0x33c
  [c1051e88] [c00322e8] bringup_nonboot_cpus+0x88/0xc8
  [c1051eb8] [c07e67bc] smp_init+0x30/0x78
  [c1051ed8] [c07d9e28] kernel_init_freeable+0x118/0x2a8
  [c1051f18] [c00032d8] kernel_init+0x14/0x124
  [c1051f38] [c0010278] ret_from_kernel_thread+0x14/0x1c

Fixes: c45361abb918 ("powerpc/85xx: fix timebase sync issue when CONFIG_HOTPLUG_CPU=n")
Reported-by: Martin Kennedy <hurricos@...il.com>
Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
Tested-by: Martin Kennedy <hurricos@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20211126041153.16926-1-nixiaoming@huawei.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/platforms/85xx/smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index 83f4a6389a282..d7081e9af65c7 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -220,7 +220,7 @@ static int smp_85xx_start_cpu(int cpu)
 	local_irq_save(flags);
 	hard_irq_disable();
 
-	if (qoriq_pm_ops)
+	if (qoriq_pm_ops && qoriq_pm_ops->cpu_up_prepare)
 		qoriq_pm_ops->cpu_up_prepare(cpu);
 
 	/* if cpu is not spinning, reset it */
@@ -292,7 +292,7 @@ static int smp_85xx_kick_cpu(int nr)
 		booting_thread_hwid = cpu_thread_in_core(nr);
 		primary = cpu_first_thread_sibling(nr);
 
-		if (qoriq_pm_ops)
+		if (qoriq_pm_ops && qoriq_pm_ops->cpu_up_prepare)
 			qoriq_pm_ops->cpu_up_prepare(nr);
 
 		/*
-- 
2.34.1