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Subject[PATCH 3.16 40/72] s390/topology: avoid firing events before kobjs are created
3.16.79-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Gorbik <gor@linux.ibm.com>

commit f3122a79a1b0a113d3aea748e0ec26f2cb2889de upstream.

arch_update_cpu_topology is first called from:
kernel_init_freeable->sched_init_smp->sched_init_domains

even before cpus has been registered in:
kernel_init_freeable->do_one_initcall->s390_smp_init

Do not trigger kobject_uevent change events until cpu devices are
actually created. Fixes the following kasan findings:

BUG: KASAN: global-out-of-bounds in kobject_uevent_env+0xb40/0xee0
Read of size 8 at addr 0000000000000020 by task swapper/0/1

BUG: KASAN: global-out-of-bounds in kobject_uevent_env+0xb36/0xee0
Read of size 8 at addr 0000000000000018 by task swapper/0/1

CPU: 0 PID: 1 Comm: swapper/0 Tainted: G B
Hardware name: IBM 3906 M04 704 (LPAR)
Call Trace:
([<0000000143c6db7e>] show_stack+0x14e/0x1a8)
[<0000000145956498>] dump_stack+0x1d0/0x218
[<000000014429fb4c>] print_address_description+0x64/0x380
[<000000014429f630>] __kasan_report+0x138/0x168
[<0000000145960b96>] kobject_uevent_env+0xb36/0xee0
[<0000000143c7c47c>] arch_update_cpu_topology+0x104/0x108
[<0000000143df9e22>] sched_init_domains+0x62/0xe8
[<000000014644c94a>] sched_init_smp+0x3a/0xc0
[<0000000146433a20>] kernel_init_freeable+0x558/0x958
[<000000014599002a>] kernel_init+0x22/0x160
[<00000001459a71d4>] ret_from_fork+0x28/0x30
[<00000001459a71dc>] kernel_thread_starter+0x0/0x10

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/s390/kernel/topology.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -266,7 +266,8 @@ int arch_update_cpu_topology(void)
update_cpu_masks();
for_each_online_cpu(cpu) {
dev = get_cpu_device(cpu);
- kobject_uevent(&dev->kobj, KOBJ_CHANGE);
+ if (dev)
+ kobject_uevent(&dev->kobj, KOBJ_CHANGE);
}
return 1;
}
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