Forwarded: Re: [syzbot] [virt?] upstream test error: KMSAN: use-after-free in vring_map_one_sg

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Subject: Re: [syzbot] [virt?] upstream test error: KMSAN: use-after-free in vring_map_one_sg
Author: jasowang@redhat.com

#syz test

On Sat, Oct 11, 2025 at 4:38 AM syzbot
<syzbot+ac856b8b866cca41352c@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    ba9dac987319 Merge tag 'libnvdimm-for-6.18' of git://git.k..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=138581e2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ad506767107aacda
> dashboard link: https://syzkaller.appspot.com/bug?extid=ac856b8b866cca41352c
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ce6a737acd38/disk-ba9dac98.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d7053b626642/vmlinux-ba9dac98.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/13f2d7e62179/bzImage-ba9dac98.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ac856b8b866cca41352c@syzkaller.appspotmail.com
>
> 8021q: adding VLAN 0 to HW filter on device bond0
> eql: remember to turn off Van-Jacobson compression on your slave devices
> =====================================================
> BUG: KMSAN: use-after-free in vring_map_one_sg+0x290/0x7b0 drivers/virtio/virtio_ring.c:401
>  vring_map_one_sg+0x290/0x7b0 drivers/virtio/virtio_ring.c:401
>  virtqueue_add_split drivers/virtio/virtio_ring.c:608 [inline]
>  virtqueue_add+0x32aa/0x6320 drivers/virtio/virtio_ring.c:2281
>  virtqueue_add_outbuf+0x89/0xa0 drivers/virtio/virtio_ring.c:2342
>  virtnet_add_outbuf drivers/net/virtio_net.c:574 [inline]
>  xmit_skb drivers/net/virtio_net.c:3343 [inline]
>  start_xmit+0x274d/0x4860 drivers/net/virtio_net.c:3367
>  __netdev_start_xmit include/linux/netdevice.h:5248 [inline]
>  netdev_start_xmit include/linux/netdevice.h:5257 [inline]
>  xmit_one net/core/dev.c:3845 [inline]
>  dev_hard_start_xmit+0x22c/0xa30 net/core/dev.c:3861
>  sch_direct_xmit+0x3b2/0xcf0 net/sched/sch_generic.c:344
>  __dev_xmit_skb net/core/dev.c:4152 [inline]
>  __dev_queue_xmit+0x3588/0x5e60 net/core/dev.c:4729
>  dev_queue_xmit include/linux/netdevice.h:3365 [inline]
>  lapbeth_data_transmit+0x352/0x480 drivers/net/wan/lapbether.c:260
>  lapb_data_transmit+0x90/0xf0 net/lapb/lapb_iface.c:447
>  lapb_transmit_buffer+0x260/0x330 net/lapb/lapb_out.c:149
>  lapb_send_control+0x458/0x5b0 net/lapb/lapb_subr.c:251
>  lapb_establish_data_link+0xa6/0xd0 net/lapb/lapb_out.c:-1
>  lapb_device_event+0xb2a/0xbc0 net/lapb/lapb_iface.c:-1
>  notifier_call_chain kernel/notifier.c:85 [inline]
>  raw_notifier_call_chain+0xe0/0x410 kernel/notifier.c:453
>  call_netdevice_notifiers_info+0x1ac/0x2b0 net/core/dev.c:2229
>  call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
>  call_netdevice_notifiers net/core/dev.c:2281 [inline]
>  __dev_notify_flags+0x20d/0x3c0 net/core/dev.c:-1
>  netif_change_flags+0x162/0x1e0 net/core/dev.c:9705
>  dev_change_flags+0x18c/0x320 net/core/dev_api.c:68
>  devinet_ioctl+0x1186/0x2500 net/ipv4/devinet.c:1199
>  inet_ioctl+0x4c0/0x6f0 net/ipv4/af_inet.c:1003
>  sock_do_ioctl+0x9c/0x480 net/socket.c:1254
>  sock_ioctl+0x70b/0xd60 net/socket.c:1375
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:597 [inline]
>  __se_sys_ioctl+0x239/0x400 fs/ioctl.c:583
>  __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:583
>  x64_sys_call+0x1cbc/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:17
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Uninit was created at:
>  slab_free_hook mm/slub.c:2440 [inline]
>  slab_free mm/slub.c:6566 [inline]
>  kmem_cache_free+0x2b0/0x1490 mm/slub.c:6676
>  skb_kfree_head net/core/skbuff.c:1046 [inline]
>  skb_free_head+0x13c/0x3a0 net/core/skbuff.c:1060
>  skb_release_data+0x9f7/0xac0 net/core/skbuff.c:1087
>  skb_release_all net/core/skbuff.c:1152 [inline]
>  __kfree_skb+0x6b/0x260 net/core/skbuff.c:1166
>  consume_skb+0x83/0x230 net/core/skbuff.c:1398
>  skb_free_datagram+0x1e/0x30 net/core/datagram.c:324
>  netlink_recvmsg+0xad1/0xfe0 net/netlink/af_netlink.c:1974
>  sock_recvmsg_nosec net/socket.c:1078 [inline]
>  sock_recvmsg+0x2dc/0x390 net/socket.c:1100
>  ____sys_recvmsg+0x193/0x610 net/socket.c:2850
>  ___sys_recvmsg+0x20b/0x850 net/socket.c:2892
>  __sys_recvmsg net/socket.c:2925 [inline]
>  __do_sys_recvmsg net/socket.c:2931 [inline]
>  __se_sys_recvmsg net/socket.c:2928 [inline]
>  __x64_sys_recvmsg+0x20e/0x3d0 net/socket.c:2928
>  x64_sys_call+0x35f0/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:48
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Bytes 0-17 of 18 are uninitialized
> Memory access of size 18 starts at ffff88811a0f1000
>
> CPU: 1 UID: 0 PID: 5441 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(none)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> =====================================================
>
>
> ---
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