linux-kernel - Re: [PATCH] security: device_cgroup: fix RCU lockdep splat

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+5PVA6j+whjzpV-e6HJKqyJwVY7Mzb6AEj2YOMfa=J29AJMjQ@mail.gmail.com>
Date:	Wed, 2 Sep 2015 08:29:14 -0400
From:	Josh Boyer <jwboyer@...oraproject.org>
To:	Felipe Balbi <balbi@...com>
Cc:	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] security: device_cgroup: fix RCU lockdep splat

On Tue, Sep 1, 2015 at 9:08 AM, Felipe Balbi <balbi@...com> wrote:
> On Tue, Sep 01, 2015 at 11:12:18AM +0200, Sebastian Ott wrote:
>> On Mon, 31 Aug 2015, Felipe Balbi wrote:
>> > while booting AM437x device, the following splat
>> > triggered:
>> >
>> > [   12.005238] ===============================
>> > [   12.009749] [ INFO: suspicious RCU usage. ]
>> > [   12.014116] 4.2.0-next-20150831 #1154 Not tainted
>> > [   12.019050] -------------------------------
>> > [   12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization!
>> > [   12.033576] other info that might help us debug this:
>> >
>> > [   12.041942] rcu_scheduler_active = 1, debug_locks = 0
>> > [   12.048796] 4 locks held by systemd/1:
>> > [   12.052700]  #0:  (sb_writers#7){.+.+.+}, at: [<c017af84>] __sb_start_write+0x8c/0xb0
>> > [   12.060954]  #1:  (&of->mutex){+.+.+.}, at: [<c01f1600>] kernfs_fop_write+0x50/0x1b8
>> > [   12.069085]  #2:  (s_active#30){++++.+}, at: [<c01f1608>] kernfs_fop_write+0x58/0x1b8
>> > [   12.077310]  #3:  (devcgroup_mutex){+.+...}, at: [<c0317bfc>] devcgroup_access_write+0x20/0x658
>> > [   12.086575] stack backtrace:
>> > [   12.091124] CPU: 0 PID: 1 Comm: systemd Not tainted 4.2.0-next-20150831 #1154
>> > [   12.098609] Hardware name: Generic AM43 (Flattened Device Tree)
>> > [   12.104807] [<c001770c>] (unwind_backtrace) from [<c0013a58>] (show_stack+0x10/0x14)
>> > [   12.112924] [<c0013a58>] (show_stack) from [<c034f014>] (dump_stack+0x84/0x9c)
>> > [   12.120491] [<c034f014>] (dump_stack) from [<c0317a04>] (verify_new_ex+0xc4/0xdc)
>> > [   12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658)
>> > [   12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc)
>> > [   12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8)
>> > [   12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8)
>> > [   12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c)
>> > [   12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c)
>> > [   12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c)
>> >
>> > Fix it by making sure rcu_read_lock() is held
>> > around devcgroup_update_access().
>>
>> With this patch applied I got the following:
>>
>> [    4.079102] BUG: sleeping function called from invalid context at mm/slub.c:1266
>> [    4.079105] in_atomic(): 0, irqs_disabled(): 0, pid: 1, name: systemd
>
> that didn't trigger here. maybe I didn't have lock debugging enabled.
> I'll have a look.

Did you happen to get a chance to poke further?  I'm seeing the
original splat on all my machines as well.

josh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/