CVE-2025-21884

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> net: better track kernel sockets lifetime<br /> <br /> While kernel sockets are dismantled during pernet_operations-&gt;exit(),<br /> their freeing can be delayed by any tx packets still held in qdisc<br /> or device queues, due to skb_set_owner_w() prior calls.<br /> <br /> This then trigger the following warning from ref_tracker_dir_exit() [1]<br /> <br /> To fix this, make sure that kernel sockets own a reference on net-&gt;passive.<br /> <br /> Add sk_net_refcnt_upgrade() helper, used whenever a kernel socket<br /> is converted to a refcounted one.<br /> <br /> [1]<br /> <br /> [ 136.263918][ T35] ref_tracker: net notrefcnt@ffff8880638f01e0 has 1/2 users at<br /> [ 136.263918][ T35] sk_alloc+0x2b3/0x370<br /> [ 136.263918][ T35] inet6_create+0x6ce/0x10f0<br /> [ 136.263918][ T35] __sock_create+0x4c0/0xa30<br /> [ 136.263918][ T35] inet_ctl_sock_create+0xc2/0x250<br /> [ 136.263918][ T35] igmp6_net_init+0x39/0x390<br /> [ 136.263918][ T35] ops_init+0x31e/0x590<br /> [ 136.263918][ T35] setup_net+0x287/0x9e0<br /> [ 136.263918][ T35] copy_net_ns+0x33f/0x570<br /> [ 136.263918][ T35] create_new_namespaces+0x425/0x7b0<br /> [ 136.263918][ T35] unshare_nsproxy_namespaces+0x124/0x180<br /> [ 136.263918][ T35] ksys_unshare+0x57d/0xa70<br /> [ 136.263918][ T35] __x64_sys_unshare+0x38/0x40<br /> [ 136.263918][ T35] do_syscall_64+0xf3/0x230<br /> [ 136.263918][ T35] entry_SYSCALL_64_after_hwframe+0x77/0x7f<br /> [ 136.263918][ T35]<br /> [ 136.343488][ T35] ref_tracker: net notrefcnt@ffff8880638f01e0 has 1/2 users at<br /> [ 136.343488][ T35] sk_alloc+0x2b3/0x370<br /> [ 136.343488][ T35] inet6_create+0x6ce/0x10f0<br /> [ 136.343488][ T35] __sock_create+0x4c0/0xa30<br /> [ 136.343488][ T35] inet_ctl_sock_create+0xc2/0x250<br /> [ 136.343488][ T35] ndisc_net_init+0xa7/0x2b0<br /> [ 136.343488][ T35] ops_init+0x31e/0x590<br /> [ 136.343488][ T35] setup_net+0x287/0x9e0<br /> [ 136.343488][ T35] copy_net_ns+0x33f/0x570<br /> [ 136.343488][ T35] create_new_namespaces+0x425/0x7b0<br /> [ 136.343488][ T35] unshare_nsproxy_namespaces+0x124/0x180<br /> [ 136.343488][ T35] ksys_unshare+0x57d/0xa70<br /> [ 136.343488][ T35] __x64_sys_unshare+0x38/0x40<br /> [ 136.343488][ T35] do_syscall_64+0xf3/0x230<br /> [ 136.343488][ T35] entry_SYSCALL_64_after_hwframe+0x77/0x7f