On Wed, Nov 09, 2022 at 04:42:13PM +0100, Stefano Garzarella wrote:
> Before commit 3d5698793897 ("vhost-vdpa: introduce asid based IOTLB")
> we call vhost_vdpa_iotlb_unmap(v, iotlb, 0ULL, 0ULL - 1) during the
> release to free all the resources allocated when processing user IOTLB
> messages through vhost_vdpa_process_iotlb_update().
> That commit changed the handling of IOTLB a bit, and we accidentally
> removed some code called during the release.
>
> We partially fixed with commit 037d4305569a ("vhost-vdpa: call
> vhost_vdpa_cleanup during the release") but a potential memory leak is
> still there as showed by kmemleak if the application does not send
> VHOST_IOTLB_INVALIDATE or crashes:
>
> unreferenced object 0xffff888007fbaa30 (size 16):
> comm "blkio-bench", pid 914, jiffies 4294993521 (age 885.500s)
> hex dump (first 16 bytes):
> 40 73 41 07 80 88 ff ff 00 00 00 00 00 00 00 00 @sA.............
> backtrace:
> [<0000000087736d2a>] kmem_cache_alloc_trace+0x142/0x1c0
> [<0000000060740f50>] vhost_vdpa_process_iotlb_msg+0x68c/0x901 [vhost_vdpa]
> [<0000000083e8e205>] vhost_chr_write_iter+0xc0/0x4a0 [vhost]
> [<000000008f2f414a>] vhost_vdpa_chr_write_iter+0x18/0x20 [vhost_vdpa]
> [<00000000de1cd4a0>] vfs_write+0x216/0x4b0
> [<00000000a2850200>] ksys_write+0x71/0xf0
> [<00000000de8e720b>] __x64_sys_write+0x19/0x20
> [<0000000018b12cbb>] do_syscall_64+0x3f/0x90
> [<00000000986ec465>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Let's fix calling vhost_vdpa_iotlb_unmap() on the whole range in
> vhost_vdpa_remove_as(). We move that call before vhost_dev_cleanup()
> since we need a valid v->vdev.mm in vhost_vdpa_pa_unmap().
> vhost_iotlb_reset() call can be removed, since vhost_vdpa_iotlb_unmap()
> on the whole range removes all the entries.
>
> The kmemleak log reported was observed with a vDPA device that has `use_va`
> set to true (e.g. VDUSE). This patch has been tested with both types of
> devices.
>
> Fixes: 037d4305569a ("vhost-vdpa: call vhost_vdpa_cleanup during the release")
> Fixes: 3d5698793897 ("vhost-vdpa: introduce asid based IOTLB")
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
It's fine, just pls don't say "potential" here in the subject, let's
avoid pleonasms - it's a memory leak, yes it triggers under some coditions
but little is unconditional in this world :)
No need to repost.
> ---
> drivers/vhost/vdpa.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 166044642fd5..b08e07fc7d1f 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -65,6 +65,10 @@ static DEFINE_IDA(vhost_vdpa_ida);
>
> static dev_t vhost_vdpa_major;
>
> +static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v,
> + struct vhost_iotlb *iotlb,
> + u64 start, u64 last);
> +
> static inline u32 iotlb_to_asid(struct vhost_iotlb *iotlb)
> {
> struct vhost_vdpa_as *as = container_of(iotlb, struct
> @@ -135,7 +139,7 @@ static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32 asid)
> return -EINVAL;
>
> hlist_del(&as->hash_link);
> - vhost_iotlb_reset(&as->iotlb);
> + vhost_vdpa_iotlb_unmap(v, &as->iotlb, 0ULL, 0ULL - 1);
> kfree(as);
>
> return 0;
> @@ -1162,14 +1166,14 @@ static void vhost_vdpa_cleanup(struct vhost_vdpa *v)
> struct vhost_vdpa_as *as;
> u32 asid;
>
> - vhost_dev_cleanup(&v->vdev);
> - kfree(v->vdev.vqs);
> -
> for (asid = 0; asid < v->vdpa->nas; asid++) {
> as = asid_to_as(v, asid);
> if (as)
> vhost_vdpa_remove_as(v, asid);
> }
> +
> + vhost_dev_cleanup(&v->vdev);
> + kfree(v->vdev.vqs);
> }
>
> static int vhost_vdpa_open(struct inode *inode, struct file *filep)
> --
> 2.38.1
