From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: Sasha Levin <Alexander.Levin@microsoft.com>,
stable <stable@vger.kernel.org>
Subject: Re: [4.9-stable] watchdog: Fix the race between the release of watchdog_core_data and cdev
Date: Thu, 21 May 2020 07:49:23 +0200 [thread overview]
Message-ID: <20200521054923.GC2295294@kroah.com> (raw)
In-Reply-To: <21124d783a72aa3292502100b1558ddf8f873b97.camel@codethink.co.uk>
On Wed, May 20, 2020 at 09:15:57PM +0100, Ben Hutchings wrote:
> On Wed, 2020-05-20 at 21:10 +0100, Ben Hutchings wrote:
> > Please queue up the attached backport of commit 2351c88f8296 "watchdog:
> > Fix the race between the release of watchdog_core_data and cdev" for
> > 4.14.
>
> And here's the corresponding version for 4.9.
>
> Ben.
>
> --
> Ben Hutchings, Software Developer Codethink Ltd
> https://www.codethink.co.uk/ Dale House, 35 Dale Street
> Manchester, M1 2HF, United Kingdom
> From 1cf1b24c844a037da38e6096a865bcab75aa05eb Mon Sep 17 00:00:00 2001
> From: Kevin Hao <haokexin@gmail.com>
> Date: Tue, 8 Oct 2019 19:29:34 +0800
> Subject: watchdog: Fix the race between the release of watchdog_core_data and
> cdev
>
> commit 72139dfa2464e43957d330266994740bb7be2535 upstream.
>
> The struct cdev is embedded in the struct watchdog_core_data. In the
> current code, we manage the watchdog_core_data with a kref, but the
> cdev is manged by a kobject. There is no any relationship between
> this kref and kobject. So it is possible that the watchdog_core_data is
> freed before the cdev is entirely released. We can easily get the
> following call trace with CONFIG_DEBUG_KOBJECT_RELEASE and
> CONFIG_DEBUG_OBJECTS_TIMERS enabled.
> ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x38
> WARNING: CPU: 23 PID: 1028 at lib/debugobjects.c:481 debug_print_object+0xb0/0xf0
> Modules linked in: softdog(-) deflate ctr twofish_generic twofish_common camellia_generic serpent_generic blowfish_generic blowfish_common cast5_generic cast_common cmac xcbc af_key sch_fq_codel openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
> CPU: 23 PID: 1028 Comm: modprobe Not tainted 5.3.0-next-20190924-yoctodev-standard+ #180
> Hardware name: Marvell OcteonTX CN96XX board (DT)
> pstate: 00400009 (nzcv daif +PAN -UAO)
> pc : debug_print_object+0xb0/0xf0
> lr : debug_print_object+0xb0/0xf0
> sp : ffff80001cbcfc70
> x29: ffff80001cbcfc70 x28: ffff800010ea2128
> x27: ffff800010bad000 x26: 0000000000000000
> x25: ffff80001103c640 x24: ffff80001107b268
> x23: ffff800010bad9e8 x22: ffff800010ea2128
> x21: ffff000bc2c62af8 x20: ffff80001103c600
> x19: ffff800010e867d8 x18: 0000000000000060
> x17: 0000000000000000 x16: 0000000000000000
> x15: ffff000bd7240470 x14: 6e6968207473696c
> x13: 5f72656d6974203a x12: 6570797420746365
> x11: 6a626f2029302065 x10: 7461747320657669
> x9 : 7463612820657669 x8 : 3378302f3078302b
> x7 : 0000000000001d7a x6 : ffff800010fd5889
> x5 : 0000000000000000 x4 : 0000000000000000
> x3 : 0000000000000000 x2 : ffff000bff948548
> x1 : 276a1c9e1edc2300 x0 : 0000000000000000
> Call trace:
> debug_print_object+0xb0/0xf0
> debug_check_no_obj_freed+0x1e8/0x210
> kfree+0x1b8/0x368
> watchdog_cdev_unregister+0x88/0xc8
> watchdog_dev_unregister+0x38/0x48
> watchdog_unregister_device+0xa8/0x100
> softdog_exit+0x18/0xfec4 [softdog]
> __arm64_sys_delete_module+0x174/0x200
> el0_svc_handler+0xd0/0x1c8
> el0_svc+0x8/0xc
>
> This is a common issue when using cdev embedded in a struct.
> Fortunately, we already have a mechanism to solve this kind of issue.
> Please see commit 233ed09d7fda ("chardev: add helper function to
> register char devs with a struct device") for more detail.
Wait, 233ed09d7fda ("chardev: add helper function to register char devs
with a struct device") only showed up in 4.12, it's not in 4.9, so how
is this needed for 4.9?
thanks,
greg k-h
prev parent reply other threads:[~2020-05-21 5:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 20:10 [4.14-stable] watchdog: Fix the race between the release of watchdog_core_data and cdev Ben Hutchings
2020-05-20 20:15 ` [4.9-stable] " Ben Hutchings
2020-05-21 5:45 ` Greg Kroah-Hartman
2020-05-21 5:49 ` Greg Kroah-Hartman [this message]
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