Patch "arm64: fix NULL dereference in have_cpu_die()" has been added to the 4.9-stable tree

Patch "arm64: fix NULL dereference in have_cpu_die()" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    arm64: fix NULL dereference in have_cpu_die()

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-fix-null-dereference-in-have_cpu_die.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 335d2c2d192266358c5dfa64953a4c162f46e464 Mon Sep 17 00:00:00 2001
From: Mark Salter <msalter@redhat.com>
Date: Fri, 24 Mar 2017 09:53:56 -0400
Subject: arm64: fix NULL dereference in have_cpu_die()

From: Mark Salter <msalter@redhat.com>

commit 335d2c2d192266358c5dfa64953a4c162f46e464 upstream.

Commit 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are
stuck in the kernel") added a helper function to determine if die() is
supported in cpu_ops. This function assumes a cpu will have a valid
cpu_ops entry, but that may not be the case for cpu0 is spin-table or
parking protocol is used to boot secondary cpus. In that case, there
is a NULL dereference if have_cpu_die() is called by cpu0. So add a
check for a valid cpu_ops before dereferencing it.

Fixes: 5c492c3f5255 ("arm64: smp: Add function to determine if cpus are stuck in the kernel")
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/kernel/smp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -934,7 +934,7 @@ static bool have_cpu_die(void)
 #ifdef CONFIG_HOTPLUG_CPU
 	int any_cpu = raw_smp_processor_id();
 
-	if (cpu_ops[any_cpu]->cpu_die)
+	if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die)
 		return true;
 #endif
 	return false;


Patches currently in stable-queue which might be from msalter@redhat.com are

queue-4.9/arm64-fix-null-dereference-in-have_cpu_die.patch