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. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
