Patch "cpu/cacheinfo: Fix teardown path" has been added to the 4.1-stable tree

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

cpu/cacheinfo: Fix teardown path

to the 4.1-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:
cpu-cacheinfo-fix-teardown-path.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Borislav Petkov <[email protected]>
Date: Sat, 8 Aug 2015 10:46:02 +0200
Subject: cpu/cacheinfo: Fix teardown path
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From: Borislav Petkov <[email protected]>

commit 2110d70c5e58326a10e93cfefdc0b3686e2ada12 upstream.

Philip Müller reported a hang when booting 32-bit 4.1 kernel on an AMD box. A fragment of the splat was enough to pinpoint the issue:

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

cache_shared_cpu_map_setup() did check sibling CPUs cacheinfo descriptor while the respective teardown path cache_shared_cpu_map_remove() didn't. Fix that.

descriptor check to free_cache_attributes(), thus cleaning up the hotplug path a little and making this even more robust.

---
 drivers/base/cacheinfo.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

@@ -148,7 +148,11 @@ static void cache_shared_cpu_map_remove(
 
 			if (sibling == cpu) /* skip itself */
 				continue;
+
 			sib_cpu_ci = get_cpu_cacheinfo(sibling);
+			if (!sib_cpu_ci->info_list)
+				continue;
+
 			sib_leaf = sib_cpu_ci->info_list + index;
 			cpumask_clear_cpu(cpu, &sib_leaf->shared_cpu_map);
 			cpumask_clear_cpu(sibling, &this_leaf->shared_cpu_map);

@@ -159,6 +163,9 @@ static void cache_shared_cpu_map_remove(
 
 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 +521,7 @@ static int cacheinfo_cpu_callback(struct
 		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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/x86-efi-fix-boot-crash-by-mapping-efi-memmap-entries-bottom-up-at-runtime-instead-of-top-down.patch queue-4.1/perf-header-fixup-reading-of-header_nrcpus-feature.patch queue-4.1/cpu-cacheinfo-fix-teardown-path.patch