linux-kernel - Re: [PATCH AUTOSEL 4.19 120/172] vfio/pci: fix memory leaks of eventfd ctx

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Date:   Wed, 17 Jun 2020 19:26:12 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Qian Cai <cai@....pw>, kvm@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.19 120/172] vfio/pci: fix memory leaks of
 eventfd ctx

On Wed, 17 Jun 2020 21:21:26 -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 66783a37f450..36b2ea920bc9 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -407,6 +407,10 @@ static void vfio_pci_release(void *device_data)
>  	if (!(--vdev->refcnt)) {
>  		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(&driver_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,
Alex