linux-kernel - Re: [PATCH AUTOSEL 5.7 280/388] vfio/pci: fix memory leaks of eventfd ctx

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Message-ID: <20200618142943.GS1931@sasha-vm>
Date:   Thu, 18 Jun 2020 10:29:43 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Qian Cai <cai@....pw>, kvm@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.7 280/388] vfio/pci: fix memory leaks of
 eventfd ctx

On Wed, Jun 17, 2020 at 07:25:01PM -0600, Alex Williamson wrote:
>On Wed, 17 Jun 2020 21:06:17 -0400
>Sasha Levin <sashal@...nel.org> wrote:
>
>> From: Qian Cai <cai@....pw>
>>
>> [ Upstream commit 1518ac272e789cae8c555d69951b032a275b7602 ]
>>
>> Finished a qemu-kvm (-device vfio-pci,host=0001:01:00.0) triggers a few
>> memory leaks after a while because vfio_pci_set_ctx_trigger_single()
>> calls eventfd_ctx_fdget() without the matching eventfd_ctx_put() later.
>> Fix it by calling eventfd_ctx_put() for those memory in
>> vfio_pci_release() before vfio_device_release().
>>
>> unreferenced object 0xebff008981cc2b00 (size 128):
>>   comm "qemu-kvm", pid 4043, jiffies 4294994816 (age 9796.310s)
>>   hex dump (first 32 bytes):
>>     01 00 00 00 6b 6b 6b 6b 00 00 00 00 ad 4e ad de  ....kkkk.....N..
>>     ff ff ff ff 6b 6b 6b 6b ff ff ff ff ff ff ff ff  ....kkkk........
>>   backtrace:
>>     [<00000000917e8f8d>] slab_post_alloc_hook+0x74/0x9c
>>     [<00000000df0f2aa2>] kmem_cache_alloc_trace+0x2b4/0x3d4
>>     [<000000005fcec025>] do_eventfd+0x54/0x1ac
>>     [<0000000082791a69>] __arm64_sys_eventfd2+0x34/0x44
>>     [<00000000b819758c>] do_el0_svc+0x128/0x1dc
>>     [<00000000b244e810>] el0_sync_handler+0xd0/0x268
>>     [<00000000d495ef94>] el0_sync+0x164/0x180
>> unreferenced object 0x29ff008981cc4180 (size 128):
>>   comm "qemu-kvm", pid 4043, jiffies 4294994818 (age 9796.290s)
>>   hex dump (first 32 bytes):
>>     01 00 00 00 6b 6b 6b 6b 00 00 00 00 ad 4e ad de  ....kkkk.....N..
>>     ff ff ff ff 6b 6b 6b 6b ff ff ff ff ff ff ff ff  ....kkkk........
>>   backtrace:
>>     [<00000000917e8f8d>] slab_post_alloc_hook+0x74/0x9c
>>     [<00000000df0f2aa2>] kmem_cache_alloc_trace+0x2b4/0x3d4
>>     [<000000005fcec025>] do_eventfd+0x54/0x1ac
>>     [<0000000082791a69>] __arm64_sys_eventfd2+0x34/0x44
>>     [<00000000b819758c>] do_el0_svc+0x128/0x1dc
>>     [<00000000b244e810>] el0_sync_handler+0xd0/0x268
>>     [<00000000d495ef94>] el0_sync+0x164/0x180
>>
>> Signed-off-by: Qian Cai <cai@....pw>
>> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  drivers/vfio/pci/vfio_pci.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 6c6b37b5c04e..080e6608f297 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -519,6 +519,10 @@ static void vfio_pci_release(void *device_data)
>>  		vfio_pci_vf_token_user_add(vdev, -1);
>>  		vfio_spapr_pci_eeh_release(vdev->pdev);
>>  		vfio_pci_disable(vdev);
>> +		if (vdev->err_trigger)
>> +			eventfd_ctx_put(vdev->err_trigger);
>> +		if (vdev->req_trigger)
>> +			eventfd_ctx_put(vdev->req_trigger);
>>  	}
>>
>>  	mutex_unlock(&vdev->reflck->lock);
>
>
>This has a fix pending, I'd suggest not picking it on its own:
>
>https://lore.kernel.org/kvm/20200616085052.sahrunsesjyjeyf2@beryllium.lan/
>https://lore.kernel.org/kvm/159234276956.31057.6902954364435481688.stgit@gimli.home/

Thanks! I'll hold off on this until the fix is in too.

-- 
Thanks,
Sasha