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Subject: Re: [PATCH 5.3 113/148] thermal: Fix use-after-free when
 unregistering thermal zone device
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org, Jiri Pirko <jiri@mellanox.com>,
        Ido Schimmel <idosch@mellanox.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Sasha Levin <sashal@kernel.org>, wvw@google.com,
        lukasz.luba@arm.com
References: <20191010083609.660878383@linuxfoundation.org>
 <20191010083617.967244655@linuxfoundation.org>
From:   Lukasz Luba <lukasz.luba@arm.com>
Message-ID: <905e26d4-76c7-555f-3b33-51fa3cf7a470@arm.com>
Date:   Thu, 14 Nov 2019 13:17:55 +0000
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Hi Greg,

This patch causes a deadlock, the thermal framework stops. Please check
this fix (I found it before posting exactly the same solution):
https://lkml.org/lkml/2019/11/12/1075

I have verified it on OdroidXU4 and it works. It needs some cleaning in
the commit message, though.
I have added to CC the author: Wei Wang

I don't know in how many stable trees it was applied, but should be fix
there also.

Regards,
Lukasz Luba

On 10/10/19 9:36 AM, Greg Kroah-Hartman wrote:
> From: Ido Schimmel <idosch@mellanox.com>
> 
> [ Upstream commit 1851799e1d2978f68eea5d9dff322e121dcf59c1 ]
> 
> thermal_zone_device_unregister() cancels the delayed work that polls the
> thermal zone, but it does not wait for it to finish. This is racy with
> respect to the freeing of the thermal zone device, which can result in a
> use-after-free [1].
> 
> Fix this by waiting for the delayed work to finish before freeing the
> thermal zone device. Note that thermal_zone_device_set_polling() is
> never invoked from an atomic context, so it is safe to call
> cancel_delayed_work_sync() that can block.
> 
> [1]
> [  +0.002221] ==================================================================
> [  +0.000064] BUG: KASAN: use-after-free in __mutex_lock+0x1076/0x11c0
> [  +0.000016] Read of size 8 at addr ffff8881e48e0450 by task kworker/1:0/17
> 
> [  +0.000023] CPU: 1 PID: 17 Comm: kworker/1:0 Not tainted 5.2.0-rc6-custom-02495-g8e73ca3be4af #1701
> [  +0.000010] Hardware name: Mellanox Technologies Ltd. MSN2100-CB2FO/SA001017, BIOS 5.6.5 06/07/2016
> [  +0.000016] Workqueue: events_freezable_power_ thermal_zone_device_check
> [  +0.000012] Call Trace:
> [  +0.000021]  dump_stack+0xa9/0x10e
> [  +0.000020]  print_address_description.cold.2+0x9/0x25e
> [  +0.000018]  __kasan_report.cold.3+0x78/0x9d
> [  +0.000016]  kasan_report+0xe/0x20
> [  +0.000016]  __mutex_lock+0x1076/0x11c0
> [  +0.000014]  step_wise_throttle+0x72/0x150
> [  +0.000018]  handle_thermal_trip+0x167/0x760
> [  +0.000019]  thermal_zone_device_update+0x19e/0x5f0
> [  +0.000019]  process_one_work+0x969/0x16f0
> [  +0.000017]  worker_thread+0x91/0xc40
> [  +0.000014]  kthread+0x33d/0x400
> [  +0.000015]  ret_from_fork+0x3a/0x50
> 
> [  +0.000020] Allocated by task 1:
> [  +0.000015]  save_stack+0x19/0x80
> [  +0.000015]  __kasan_kmalloc.constprop.4+0xc1/0xd0
> [  +0.000014]  kmem_cache_alloc_trace+0x152/0x320
> [  +0.000015]  thermal_zone_device_register+0x1b4/0x13a0
> [  +0.000015]  mlxsw_thermal_init+0xc92/0x23d0
> [  +0.000014]  __mlxsw_core_bus_device_register+0x659/0x11b0
> [  +0.000013]  mlxsw_core_bus_device_register+0x3d/0x90
> [  +0.000013]  mlxsw_pci_probe+0x355/0x4b0
> [  +0.000014]  local_pci_probe+0xc3/0x150
> [  +0.000013]  pci_device_probe+0x280/0x410
> [  +0.000013]  really_probe+0x26a/0xbb0
> [  +0.000013]  driver_probe_device+0x208/0x2e0
> [  +0.000013]  device_driver_attach+0xfe/0x140
> [  +0.000013]  __driver_attach+0x110/0x310
> [  +0.000013]  bus_for_each_dev+0x14b/0x1d0
> [  +0.000013]  driver_register+0x1c0/0x400
> [  +0.000015]  mlxsw_sp_module_init+0x5d/0xd3
> [  +0.000014]  do_one_initcall+0x239/0x4dd
> [  +0.000013]  kernel_init_freeable+0x42b/0x4e8
> [  +0.000012]  kernel_init+0x11/0x18b
> [  +0.000013]  ret_from_fork+0x3a/0x50
> 
> [  +0.000015] Freed by task 581:
> [  +0.000013]  save_stack+0x19/0x80
> [  +0.000014]  __kasan_slab_free+0x125/0x170
> [  +0.000013]  kfree+0xf3/0x310
> [  +0.000013]  thermal_release+0xc7/0xf0
> [  +0.000014]  device_release+0x77/0x200
> [  +0.000014]  kobject_put+0x1a8/0x4c0
> [  +0.000014]  device_unregister+0x38/0xc0
> [  +0.000014]  thermal_zone_device_unregister+0x54e/0x6a0
> [  +0.000014]  mlxsw_thermal_fini+0x184/0x35a
> [  +0.000014]  mlxsw_core_bus_device_unregister+0x10a/0x640
> [  +0.000013]  mlxsw_devlink_core_bus_device_reload+0x92/0x210
> [  +0.000015]  devlink_nl_cmd_reload+0x113/0x1f0
> [  +0.000014]  genl_family_rcv_msg+0x700/0xee0
> [  +0.000013]  genl_rcv_msg+0xca/0x170
> [  +0.000013]  netlink_rcv_skb+0x137/0x3a0
> [  +0.000012]  genl_rcv+0x29/0x40
> [  +0.000013]  netlink_unicast+0x49b/0x660
> [  +0.000013]  netlink_sendmsg+0x755/0xc90
> [  +0.000013]  __sys_sendto+0x3de/0x430
> [  +0.000013]  __x64_sys_sendto+0xe2/0x1b0
> [  +0.000013]  do_syscall_64+0xa4/0x4d0
> [  +0.000013]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> [  +0.000017] The buggy address belongs to the object at ffff8881e48e0008
>                 which belongs to the cache kmalloc-2k of size 2048
> [  +0.000012] The buggy address is located 1096 bytes inside of
>                 2048-byte region [ffff8881e48e0008, ffff8881e48e0808)
> [  +0.000007] The buggy address belongs to the page:
> [  +0.000012] page:ffffea0007923800 refcount:1 mapcount:0 mapping:ffff88823680d0c0 index:0x0 compound_mapcount: 0
> [  +0.000020] flags: 0x200000000010200(slab|head)
> [  +0.000019] raw: 0200000000010200 ffffea0007682008 ffffea00076ab808 ffff88823680d0c0
> [  +0.000016] raw: 0000000000000000 00000000000d000d 00000001ffffffff 0000000000000000
> [  +0.000007] page dumped because: kasan: bad access detected
> 
> [  +0.000012] Memory state around the buggy address:
> [  +0.000012]  ffff8881e48e0300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000012]  ffff8881e48e0380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000012] >ffff8881e48e0400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000008]                                                  ^
> [  +0.000012]  ffff8881e48e0480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000012]  ffff8881e48e0500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  +0.000007] ==================================================================
> 
> Fixes: b1569e99c795 ("ACPI: move thermal trip handling to generic thermal layer")
> Reported-by: Jiri Pirko <jiri@mellanox.com>
> Signed-off-by: Ido Schimmel <idosch@mellanox.com>
> Acked-by: Jiri Pirko <jiri@mellanox.com>
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   drivers/thermal/thermal_core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 6bab66e84eb58..ebe15f2cf7fc3 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -304,7 +304,7 @@ static void thermal_zone_device_set_polling(struct thermal_zone_device *tz,
>   				 &tz->poll_queue,
>   				 msecs_to_jiffies(delay));
>   	else
> -		cancel_delayed_work(&tz->poll_queue);
> +		cancel_delayed_work_sync(&tz->poll_queue);
>   }
>   
>   static void monitor_thermal_zone(struct thermal_zone_device *tz)
>