From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sd0109e.au.ibm.com (d23rh905.au.ibm.com [202.81.18.225]) by e23smtp01.au.ibm.com (8.13.1/8.13.1) with ESMTP id m7J3c2wU032617 for ; Tue, 19 Aug 2008 13:38:02 +1000 Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by sd0109e.au.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m7J3bgGT192636 for ; Tue, 19 Aug 2008 13:37:42 +1000 Received: from d23av03.au.ibm.com (loopback [127.0.0.1]) by d23av03.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m7J3bffN011039 for ; Tue, 19 Aug 2008 13:37:42 +1000 Message-ID: <48AA4003.5080300@linux.vnet.ibm.com> Date: Tue, 19 Aug 2008 09:07:39 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com MIME-Version: 1.0 Subject: Re: [PATCH 1/1] mm_owner: fix cgroup null dereference References: <1218745013-9537-1-git-send-email-jirislaby@gmail.com> <48A49C78.7070100@linux.vnet.ibm.com> <48A9E82E.3060009@gmail.com> In-Reply-To: <48A9E82E.3060009@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Jiri Slaby Cc: Andrew Morton , containers@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Jiri Slaby wrote: > On 08/14/2008 10:58 PM, Balbir Singh wrote: >> Jiri Slaby wrote: >>> Hi, >>> >>> found this in mmotm, a fix for >>> mm-owner-fix-race-between-swap-and-exit.patch >>> >> Thanks for catching this > > Hmm, unfortunately there is one more issue with this patch. > memrlimit_cgroup_subsys doesn't expect NULL new cgroup and NULL task. > memrlimit_cgroup_mm_owner_changed blows up (called from > cgroup_mm_owner_callbacks as ss->mm_owner_changed). > > I'm out for few days, please solve it somehow. Full oops message follows. > Could you please help me with the steps to reproduce the problem. I don't seem to be hitting the mm->owner changed callback. I did have a test case for it when I developed mm->owner functionality, but it does not trigger an oops for me. > BUG: unable to handle kernel NULL pointer dereference at 00000000000004ac > IP: [] _spin_lock+0x9/0x20 > PGD 3ef84067 PUD 0 > Oops: 0002 [2] SMP > last sysfs file: /sys/devices/platform/coretemp.1/temp1_input > CPU 0 > Modules linked in: usblp ath5k mac80211 cfg80211 arc4 ecb cryptomgr aead > crypto_blkcipher crypto_algapi usbhid ohci1394 hid led_class ieee1394 evdev > rtc_cmos floppy ff_memless [last unloaded: cfg80211] > Pid: 27360, comm: automount Tainted: G D W 2.6.27-rc3-mm1_64 #441 > RIP: 0010:[] [] _spin_lock+0x9/0x20 > RSP: 0018:ffff88007839fd98 EFLAGS: 00010282 > RAX: 0000000000000100 RBX: 0000000000000000 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffffffff807d5f28 RDI: 00000000000004ac > RBP: ffff88007839fd98 R08: 00000000cc62b515 R09: 00000000f8f36e74 > R10: 0000000000000001 R11: 0000000000000000 R12: 00000000000004ac > R13: ffffffff807d5f28 R14: ffff880047e2e500 R15: ffff880047e2e680 > FS: 00007fca50fa66f0(0000) GS:ffffffff8070a480(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: 00000000000004ac CR3: 000000004510f000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process automount (pid: 27360, threadinfo ffff88007839e000, task ffff880047e2e500) > Stack: ffff88007839fdb8 ffffffff80238ab3 ffffffff80589750 0000000000000000 > ffff88007839fde8 ffffffff802b3f4b ffff8800010205b0 ffffffff80589750 > 0000000000000000 0000000000000000 ffff88007839fe18 ffffffff80270446 > Call Trace: > [] get_task_mm+0x23/0x60 > [] memrlimit_cgroup_mm_owner_changed+0x1b/0x80 > [] cgroup_mm_owner_callbacks+0x76/0x90 > [] mm_update_next_owner+0x1c4/0x240 > [] exit_mm+0x10a/0x150 > [] do_exit+0x1dc/0x940 > [] ? wake_up_state+0xb/0x10 > [] ? signal_wake_up+0x38/0x40 > [] do_group_exit+0x40/0xb0 > [] sys_exit_group+0x12/0x20 > [] system_call_fastpath+0x16/0x1b > Code: 00 00 55 48 89 e5 fa f0 81 2f 00 00 00 01 74 05 e8 dd 17 de ff c9 c3 66 66 > 2e 0f 1f 84 00 00 00 00 00 55 b8 00 01 00 00 48 89 e5 66 0f c1 07 38 e0 74 > 06 f3 90 8a 07 eb f6 c9 c3 66 0f 1f 44 > RIP [] _spin_lock+0x9/0x20 > RSP > CR2: 00000000000004ac > ---[ end trace 4eaa2a86a8e2da22 ]--- -- Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org