pfcp: fix socket lifetime on netdevice registration failure

Overview

In the Linux kernel, the following vulnerability has been resolved:

pfcp: fix socket lifetime on netdevice registration failure

pfcp_newlink() creates the UDP socket before register_netdevice(). If registration fails after pfcp_dev_init() succeeds, the core calls pfcp_dev_uninit(), which releases the socket and clears pfcp->sk. The newlink error path then releases it again, causing a NULL pointer dereference. This was observed with failslab fault injection:

FAULT_INJECTION: forcing a failure. kobject: kobject_add_internal failed for pfcp0 (error: -12 parent: net) BUG: KASAN: null-ptr-deref in udp_tunnel_sock_release+0x1c/0x50 Read of size 8 at addr 0000000000000120 by task ip/1037 Call trace: show_stack+0x18/0x24 (C) dump_stack_lvl+0x78/0x90 print_report+0x468/0x5cc kasan_report+0xa4/0xf0 __asan_load8+0x7c/0xd0 udp_tunnel_sock_release+0x1c/0x50 pfcp_newlink+0x128/0x184 rtnl_newlink+0x848/0xe44 rtnetlink_rcv_msg+0x468/0x514 netlink_rcv_skb+0xc0/0x1f0 rtnetlink_rcv+0x18/0x24 netlink_unicast+0x4b8/0x558 netlink_sendmsg+0x2b8/0x584 ...

Return from pfcp_del_sock() if pfcp->sk is NULL.

Affected

• Linux >= 76c8764ef36a5d37ea2e551bda28ac7f028383ba < dcb8f6a79c3360a440c399d85df465a6e59351f1
• Linux >= 76c8764ef36a5d37ea2e551bda28ac7f028383ba < 4b8ce1686dea1a10805a0807bf492409b0300ee1
• Linux >= 76c8764ef36a5d37ea2e551bda28ac7f028383ba < 2cee3603ec1d9b5ec7f2121ea3efe9488e906f46
• Linux >= 76c8764ef36a5d37ea2e551bda28ac7f028383ba < 0f17d2e3dd9cda3ee6d94033d5e5489af168920d
• Linux 6.10

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.