Messages in this thread | | | Date | Fri, 28 Sep 2012 14:04:23 +0800 | From | Ni zhan Chen <> | Subject | Re: [PATCH 1/4] memory-hotplug: add memory_block_release |
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On 09/28/2012 11:45 AM, Yasuaki Ishimatsu wrote: > Hi Kosaki-san, > > 2012/09/28 10:35, KOSAKI Motohiro wrote: >> On Thu, Sep 27, 2012 at 8:24 PM, Yasuaki Ishimatsu >> <isimatu.yasuaki@jp.fujitsu.com> wrote: >>> Hi Chen, >>> >>> >>> 2012/09/27 19:20, Ni zhan Chen wrote: >>>> >>>> Hi Congyang, >>>> >>>> 2012/9/27 <wency@cn.fujitsu.com> >>>> >>>>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> >>>>> >>>>> When calling remove_memory_block(), the function shows following >>>>> message >>>>> at >>>>> device_release(). >>>>> >>>>> Device 'memory528' does not have a release() function, it is >>>>> broken and >>>>> must >>>>> be fixed. >>>>> >>>> >>>> What's the difference between the patch and original implemetation? >>> >>> >>> The implementation is for removing a memory_block. So the purpose is >>> same as original one. But original code is bad manner. >>> kobject_cleanup() >>> is called by remove_memory_block() at last. But release function for >>> releasing memory_block is not registered. As a result, the kernel >>> message >>> is shown. IMHO, memory_block should be release by the releae function. >> >> but your patch introduced use after free bug, if i understand correctly. >> See unregister_memory() function. After your patch, kobject_put() call >> release_memory_block() and kfree(). and then device_unregister() will >> touch freed memory. >
this patch is similiar to [RFC v9 PATCH 10/21] memory-hotplug: add memory_block_release, they handle the same issue, can these two patches be fold to one?
> It is not correct. The kobject_put() is prepared against > find_memory_block() > in remove_memory_block() since kobject->kref is incremented in it. > So release_memory_block() is called by device_unregister() correctly > as follows: > > [ 1014.589008] Pid: 126, comm: kworker/0:2 Not tainted > 3.6.0-rc3-enable-memory-hotremove-and-root-bridge #3 > [ 1014.702437] Call Trace: > [ 1014.731684] [<ffffffff8144d096>] release_memory_block+0x16/0x30 > [ 1014.803581] [<ffffffff81438587>] device_release+0x27/0xa0 > [ 1014.869312] [<ffffffff8133e962>] kobject_cleanup+0x82/0x1b0 > [ 1014.937062] [<ffffffff8133ea9d>] kobject_release+0xd/0x10 > [ 1015.002718] [<ffffffff8133e7ec>] kobject_put+0x2c/0x60 > [ 1015.065271] [<ffffffff81438107>] put_device+0x17/0x20 > [ 1015.126794] [<ffffffff8143918a>] device_unregister+0x2a/0x60 > [ 1015.195578] [<ffffffff8144d55b>] remove_memory_block+0xbb/0xf0 > [ 1015.266434] [<ffffffff8144d5af>] unregister_memory_section+0x1f/0x30 > [ 1015.343532] [<ffffffff811c0a58>] __remove_section+0x68/0x110 > [ 1015.412318] [<ffffffff811c0be7>] __remove_pages+0xe7/0x120 > [ 1015.479021] [<ffffffff81653d8c>] arch_remove_memory+0x2c/0x80 > [ 1015.548845] [<ffffffff8165497b>] remove_memory+0x6b/0xd0 > [ 1015.613474] [<ffffffff813d946c>] > acpi_memory_device_remove_memory+0x48/0x73 > [ 1015.697834] [<ffffffff813d94c2>] acpi_memory_device_remove+0x2b/0x44 > [ 1015.774922] [<ffffffff813a61e4>] acpi_device_remove+0x90/0xb2 > [ 1015.844796] [<ffffffff8143c2fc>] __device_release_driver+0x7c/0xf0 > [ 1015.919814] [<ffffffff8143c47f>] device_release_driver+0x2f/0x50 > [ 1015.992753] [<ffffffff813a70dc>] acpi_bus_remove+0x32/0x6d > [ 1016.059462] [<ffffffff813a71a8>] acpi_bus_trim+0x91/0x102 > [ 1016.125128] [<ffffffff813a72a1>] > acpi_bus_hot_remove_device+0x88/0x16b > [ 1016.204295] [<ffffffff813a2e57>] acpi_os_execute_deferred+0x27/0x34 > [ 1016.280350] [<ffffffff81090599>] process_one_work+0x219/0x680 > [ 1016.350173] [<ffffffff81090538>] ? process_one_work+0x1b8/0x680 > [ 1016.422072] [<ffffffff813a2e30>] ? > acpi_os_wait_events_complete+0x23/0x23 > [ 1016.504357] [<ffffffff810923ce>] worker_thread+0x12e/0x320 > [ 1016.571064] [<ffffffff810922a0>] ? manage_workers+0x110/0x110 > [ 1016.640886] [<ffffffff810983a6>] kthread+0xc6/0xd0 > [ 1016.699290] [<ffffffff8167b144>] kernel_thread_helper+0x4/0x10 > [ 1016.770149] [<ffffffff81670bb0>] ? retint_restore_args+0x13/0x13 > [ 1016.843165] [<ffffffff810982e0>] ? __init_kthread_worker+0x70/0x70 > [ 1016.918200] [<ffffffff8167b140>] ? gs_change+0x13/0x13 > > Thanks, > Yasuaki Ishimatsu > >> >> static void >> unregister_memory(struct memory_block *memory) >> { >> BUG_ON(memory->dev.bus != &memory_subsys); >> >> /* drop the ref. we got in remove_memory_block() */ >> kobject_put(&memory->dev.kobj); >> device_unregister(&memory->dev); >> } >> > > >
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