From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Thu, 18 May 2017 11:04:16 +0000 (+0200)
Subject: s390/smp: fix false positive kmemleak of mcesa data structure
X-Git-Tag: v4.13-rc1~192^2~32
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9cf8edb7a33b7689d4c3429b1d339d29e7c3db86;p=karo-tx-linux.git

s390/smp: fix false positive kmemleak of mcesa data structure

I get number of CPUs - 1 kmemleak hits like

unreferenced object 0x37ec6f000 (size 1024):
  comm "swapper/0", pid 1, jiffies 4294937330 (age 889.690s)
  hex dump (first 32 bytes):
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  backtrace:
    [<000000000034a848>] kmem_cache_alloc+0x2b8/0x3d0
    [<00000000001164de>] __cpu_up+0x456/0x488
    [<000000000016f60c>] bringup_cpu+0x4c/0xd0
    [<000000000016d5d2>] cpuhp_invoke_callback+0xe2/0x9e8
    [<000000000016f3c6>] cpuhp_up_callbacks+0x5e/0x110
    [<000000000016f988>] _cpu_up+0xe0/0x158
    [<000000000016faf0>] do_cpu_up+0xf0/0x110
    [<0000000000dae1ee>] smp_init+0x126/0x130
    [<0000000000d9bd04>] kernel_init_freeable+0x174/0x2e0
    [<000000000089fc62>] kernel_init+0x2a/0x148
    [<00000000008adce2>] kernel_thread_starter+0x6/0xc
    [<00000000008adcdc>] kernel_thread_starter+0x0/0xc
    [<ffffffffffffffff>] 0xffffffffffffffff

The pointer of this data structure is stored in the prefix page of that
CPU together with some extra bits ORed into the the low bits.
Mark the data structure as non-leak.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 363000a77ffc..1020a11a24e5 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -26,6 +26,7 @@
 #include <linux/err.h>
 #include <linux/spinlock.h>
 #include <linux/kernel_stat.h>
+#include <linux/kmemleak.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/irqflags.h>
@@ -207,6 +208,8 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
 				kmem_cache_alloc(pcpu_mcesa_cache, GFP_KERNEL);
 			if (!mcesa_origin)
 				goto out;
+			/* The pointer is stored with mcesa_bits ORed in */
+			kmemleak_not_leak((void *) mcesa_origin);
 			mcesa_bits = MACHINE_HAS_GS ? 11 : 0;
 		}
 	} else {