CVE-2021-47222

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> net: bridge: fix vlan tunnel dst refcnt when egressing<br /> <br /> The egress tunnel code uses dst_clone() and directly sets the result<br /> which is wrong because the entry might have 0 refcnt or be already deleted,<br /> causing number of problems. It also triggers the WARN_ON() in dst_hold()[1]<br /> when a refcnt couldn&amp;#39;t be taken. Fix it by using dst_hold_safe() and<br /> checking if a reference was actually taken before setting the dst.<br /> <br /> [1] dmesg WARN_ON log and following refcnt errors<br /> WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]<br /> Modules linked in: 8021q garp mrp bridge stp llc bonding ipv6 virtio_net<br /> CPU: 5 PID: 38 Comm: ksoftirqd/5 Kdump: loaded Tainted: G W 5.13.0-rc3+ #360<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014<br /> RIP: 0010:br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]<br /> Code: e8 85 bc 01 e1 45 84 f6 74 90 45 31 f6 85 db 48 c7 c7 a0 02 19 a0 41 0f 94 c6 31 c9 31 d2 44 89 f6 e8 64 bc 01 e1 85 db 75 02 0b 31 c9 31 d2 44 89 f6 48 c7 c7 70 02 19 a0 e8 4b bc 01 e1 49<br /> RSP: 0018:ffff8881003d39e8 EFLAGS: 00010246<br /> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000<br /> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffa01902a0<br /> RBP: ffff8881040c6700 R08: 0000000000000000 R09: 0000000000000001<br /> R10: 2ce93d0054fe0d00 R11: 54fe0d00000e0000 R12: ffff888109515000<br /> R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000401<br /> FS: 0000000000000000(0000) GS:ffff88822bf40000(0000) knlGS:0000000000000000<br /> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> CR2: 00007f42ba70f030 CR3: 0000000109926000 CR4: 00000000000006e0<br /> Call Trace:<br /> br_handle_vlan+0xbc/0xca [bridge]<br /> __br_forward+0x23/0x164 [bridge]<br /> deliver_clone+0x41/0x48 [bridge]<br /> br_handle_frame_finish+0x36f/0x3aa [bridge]<br /> ? skb_dst+0x2e/0x38 [bridge]<br /> ? br_handle_ingress_vlan_tunnel+0x3e/0x1c8 [bridge]<br /> ? br_handle_frame_finish+0x3aa/0x3aa [bridge]<br /> br_handle_frame+0x2c3/0x377 [bridge]<br /> ? __skb_pull+0x33/0x51<br /> ? vlan_do_receive+0x4f/0x36a<br /> ? br_handle_frame_finish+0x3aa/0x3aa [bridge]<br /> __netif_receive_skb_core+0x539/0x7c6<br /> ? __list_del_entry_valid+0x16e/0x1c2<br /> __netif_receive_skb_list_core+0x6d/0xd6<br /> netif_receive_skb_list_internal+0x1d9/0x1fa<br /> gro_normal_list+0x22/0x3e<br /> dev_gro_receive+0x55b/0x600<br /> ? detach_buf_split+0x58/0x140<br /> napi_gro_receive+0x94/0x12e<br /> virtnet_poll+0x15d/0x315 [virtio_net]<br /> __napi_poll+0x2c/0x1c9<br /> net_rx_action+0xe6/0x1fb<br /> __do_softirq+0x115/0x2d8<br /> run_ksoftirqd+0x18/0x20<br /> smpboot_thread_fn+0x183/0x19c<br /> ? smpboot_unregister_percpu_thread+0x66/0x66<br /> kthread+0x10a/0x10f<br /> ? kthread_mod_delayed_work+0xb6/0xb6<br /> ret_from_fork+0x22/0x30<br /> ---[ end trace 49f61b07f775fd2b ]---<br /> dst_release: dst:00000000c02d677a refcnt:-1<br /> dst_release underflow