linux-kernel - Re: [linux41] regression with 'x86/cacheinfo: Move cacheinfo sysfs code to generic infrastructure' on AMD i686

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Date:	Sun, 26 Jul 2015 10:13:45 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Philip Müller <philm@...jaro.org>
cc:	linux-kernel@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>,
	Guenter Roeck <linux@...ck-us.net>, manjaro-dev@...jaro.org,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andre Przywara <andre.przywara@....com>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [linux41] regression with 'x86/cacheinfo: Move cacheinfo sysfs
 code to generic infrastructure' on AMD i686

On Sun, 26 Jul 2015, Philip Müller wrote:
> > task: f58e0000 ti: f58e8000 task.ti: f58e800
> > EIP: 0060:[<c135a903>] EFLAGS: 00010206 CPU: 0
> > EIP is at free_cache_attributes+0x83/0xd0
> > EAX: 00000001 EBX: f589d46c ECX: 00000090 EDX: 360c2000
> > ESI: 00000000 EDI: c1724a80 EBP: f58e9ec0 ESP: f58e9ea0
> >  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> > CR0: 8005003b CR2: 000000ac CR3: 01731000 CR4: 000006d0

That's a trivial NULL pointer dereference in the error/cleanup
path. Patch below should fix it.

Thanks,

	tglx
---
diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 764280a91776..f09b106d8b81 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -159,6 +159,9 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 
 static void free_cache_attributes(unsigned int cpu)
 {
+	if (!per_cpu_cacheinfo(cpu))
+		return;
+
 	cache_shared_cpu_map_remove(cpu);
 
 	kfree(per_cpu_cacheinfo(cpu));
@@ -514,8 +517,7 @@ static int cacheinfo_cpu_callback(struct notifier_block *nfb,
 		break;
 	case CPU_DEAD:
 		cache_remove_dev(cpu);
-		if (per_cpu_cacheinfo(cpu))
-			free_cache_attributes(cpu);
+		free_cache_attributes(cpu);
 		break;
 	}
 	return notifier_from_errno(rc);