On Fri, Mar 09, 2018 at 10:30:17AM +0800, Jason Wang wrote: > > > On 2018年03月09日 00:00, Michael S. Tsirkin wrote: > > On Thu, Mar 08, 2018 at 04:55:39PM +0100, Alexander Potapenko wrote: > > > On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > > > On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote: > > > > > KMSAN reported a use of uninit memory in vhost_net_buf_unproduce() > > > > > while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring: > > > > > > > > > > ================================================================== > > > > > BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho > > > > > et.c:170 > > > > > CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853 > > > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 > > > > > Call Trace: > > > > > __dump_stack lib/dump_stack.c:17 [inline] > > > > > dump_stack+0x185/0x1d0 lib/dump_stack.c:53 > > > > > kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093 > > > > > __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676 > > > > > vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170 > > > > > vhost_net_stop_vq drivers/vhost/net.c:974 [inline] > > > > > vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982 > > > > > vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015 > > > > > __fput+0x49f/0xa00 fs/file_table.c:209 > > > > > ____fput+0x37/0x40 fs/file_table.c:243 > > > > > task_work_run+0x243/0x2c0 kernel/task_work.c:113 > > > > > tracehook_notify_resume include/linux/tracehook.h:191 [inline] > > > > > exit_to_usermode_loop arch/x86/entry/common.c:166 [inline] > > > > > prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196 > > > > > syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265 > > > > > do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292 > > > > > ... > > > > > origin: > > > > > kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline] > > > > > kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213 > > > > > kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392 > > > > > kmalloc_large_node_hook mm/slub.c:1366 [inline] > > > > > kmalloc_large_node mm/slub.c:3808 [inline] > > > > > __kmalloc_node+0x100e/0x1290 mm/slub.c:3818 > > > > > kmalloc_node include/linux/slab.h:554 [inline] > > > > > kvmalloc_node+0x1a5/0x2e0 mm/util.c:419 > > > > > kvmalloc include/linux/mm.h:541 [inline] > > > > > vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921 > > > > > misc_open+0x7b5/0x8b0 drivers/char/misc.c:154 > > > > > chrdev_open+0xc28/0xd90 fs/char_dev.c:417 > > > > > do_dentry_open+0xccb/0x1430 fs/open.c:752 > > > > > vfs_open+0x272/0x2e0 fs/open.c:866 > > > > > do_last fs/namei.c:3378 [inline] > > > > > path_openat+0x49ad/0x6580 fs/namei.c:3519 > > > > > do_filp_open+0x267/0x640 fs/namei.c:3553 > > > > > do_sys_open+0x6ad/0x9c0 fs/open.c:1059 > > > > > SYSC_openat+0xc7/0xe0 fs/open.c:1086 > > > > > SyS_openat+0x63/0x90 fs/open.c:1080 > > > > > do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287 > > > > > ================================================================== > > > > > > > > > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > > > > --- > > > > > drivers/vhost/net.c | 1 + > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > > > index 610cba276d47..60f1080bffc7 100644 > > > > > --- a/drivers/vhost/net.c > > > > > +++ b/drivers/vhost/net.c > > > > > @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f) > > > > > n->vqs[i].done_idx = 0; > > > > > n->vqs[i].vhost_hlen = 0; > > > > > n->vqs[i].sock_hlen = 0; > > > > > + n->vqs[i].rx_ring = NULL; > > > > > vhost_net_buf_init(&n->vqs[i].rxq); > > > > > } > > > > > vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX); > > > > > -- > > > > > 2.16.2.395.g2e18187dfd-goog > > > > > > > > I suspect that's not sufficient. rx ring is tied to the tap device. > > > > I think we need to drop it every time we drop the device. > > > Unfortunately I've no idea where is the device dropped. Are you > > > referring to vhost_net_vq_reset()? > > > I can fix that part if needed, but won't be able to validate it with KMSAN. > > I see several issues. For example in vhost_net_set_backend > > if there's a value then rx ring will point to the > > ring of the wrong socket. > > Something like the below might help but we really need > > documentation of when is rx_ring valid. Is it only valid > > when private-data is valid? > > I think so, we need keep rx_ring synced with private_data. > > > If yes need to make sure > > we reset it with private_data. > > > > Also I see __skb_array_destroy_skb used with ptr_ring which > > seems suspicious: how do we know the entries are skbs? > > Good catch, will post an independent patch to fix this. > > > > > Patch below is on top of yours, and > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > > But I really would like Jason to look and come up with a > > patch to address all these issues. > > > > --- > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > index 610cba2..7a65b69 100644 > > --- a/drivers/vhost/net.c > > +++ b/drivers/vhost/net.c > > @@ -972,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n, > > vhost_net_disable_vq(n, vq); > > vq->private_data = NULL; > > vhost_net_buf_unproduce(nvq); > > + vq->rx_ring = NULL; > > mutex_unlock(&vq->mutex); > > return sock; > > } > > @@ -1161,8 +1163,6 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > vhost_net_disable_vq(n, vq); > > vq->private_data = sock; > > vhost_net_buf_unproduce(nvq); > > - if (index == VHOST_NET_VQ_RX) > > - nvq->rx_ring = get_tap_ptr_ring(fd); > > r = vhost_vq_init_access(vq); > > if (r) > > goto err_used; > > @@ -1172,6 +1172,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > oldubufs = nvq->ubufs; > > nvq->ubufs = ubufs; > > + if (index == VHOST_NET_VQ_RX) > > + nvq->rx_ring = get_tap_ptr_ring(fd); > > + else > > + nvq->rx_ring = NULL; > > Any reason to move those after vhost_net_enable_vq()? Otherwise I see an issue if there is an error and we revert the change. > And consider we won't > try to assign rx_ring to TX, the "else" part seems unnecessary. > > Thanks ok, pls pack up all fixes as you see fit and post a patchset. > > n->tx_packets = 0; > > n->tx_zcopy_err = 0;
