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Tsirkin" To: Stefano Garzarella Cc: virtualization@lists.linux-foundation.org, eperezma@redhat.com, netdev@vger.kernel.org, kvm@vger.kernel.org, Gautam Dawar , Jason Wang , linux-kernel@vger.kernel.org Subject: Re: [PATCH] vhost-vdpa: fix potential memory leak during the release Message-ID: <20221109124430-mutt-send-email-mst@kernel.org> References: <20221109154213.146789-1-sgarzare@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221109154213.146789-1-sgarzare@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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