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

Alex Williamson
2020-06-18T01:53:36Z

On Wed, 17 Jun 2020 21:21:26 -0400
Sasha Levin <sashal@kernel.org> wrote:

> From: Qian Cai <cai@lca.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@lca.pw>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.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