[tip:x86/urgent] x86/cpu/cacheinfo: Fix teardown path

[tip-bot for Borislav Petkov]

Commit-ID:  680ac028240f8747f31c03986fbcf18b2b521e93
Gitweb:     http://git.kernel.org/tip/680ac028240f8747f31c03986fbcf18b2b521e93
Author:     Borislav Petkov <bp@xxxxxxx>
AuthorDate: Mon, 27 Jul 2015 09:58:05 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 5 Aug 2015 10:08:17 +0200

x86/cpu/cacheinfo: Fix teardown path

Philip MÃller 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.

>From tglx's version: to be on the safe side, move the cacheinfo
descriptor check to free_cache_attributes(), thus cleaning up
the hotplug path a little and making this even more robust.

Reported-by: Philip MÃller <philm@xxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.1+
Cc: Andre Przywara <andre.przywara@xxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: manjaro-dev@xxxxxxxxxxx
Link: http://lkml.kernel.org/r/20150727075805.GA20416@xxxxxxxxxxx
Link: https://lkml.kernel.org/r/55B47BB8.6080202@xxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 drivers/base/cacheinfo.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 764280a..e9fd32e 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -148,7 +148,11 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 
 			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(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 +521,7 @@ 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);
--
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