Amazon Linux AMI: CVE-2024-56642: Security patch for kernel (ALAS-2025-1961)

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

tipc: Fix use-after-free of kernel socket in cleanup_bearer().

syzkaller reported a use-after-free of UDP kernel socket

in cleanup_bearer() without repro. [0][1]

When bearer_disable() calls tipc_udp_disable(), cleanup

of the UDP kernel socket is deferred by work calling

cleanup_bearer().

tipc_exit_net() waits for such works to finish by checking

tipc_net(net)->wq_count. However, the work decrements the

count too early before releasing the kernel socket,

unblocking cleanup_net() and resulting in use-after-free.

Let's move the decrement after releasing the socket in

cleanup_bearer().

[0]:

ref_tracker: net notrefcnt@000000009b3d1faf has 1/1 users at

sk_alloc+0x438/0x608

inet_create+0x4c8/0xcb0

__sock_create+0x350/0x6b8

sock_create_kern+0x58/0x78

udp_sock_create4+0x68/0x398

udp_sock_create+0x88/0xc8

tipc_udp_enable+0x5e8/0x848

__tipc_nl_bearer_enable+0x84c/0xed8

tipc_nl_bearer_enable+0x38/0x60

genl_family_rcv_msg_doit+0x170/0x248

genl_rcv_msg+0x400/0x5b0

netlink_rcv_skb+0x1dc/0x398

genl_rcv+0x44/0x68

netlink_unicast+0x678/0x8b0

netlink_sendmsg+0x5e4/0x898

____sys_sendmsg+0x500/0x830

[1]:

BUG: KMSAN: use-after-free in udp_hashslot include/net/udp.h:85 [inline]

BUG: KMSAN: use-after-free in udp_lib_unhash+0x3b8/0x930 net/ipv4/udp.c:1979

udp_hashslot include/net/udp.h:85 [inline]

udp_lib_unhash+0x3b8/0x930 net/ipv4/udp.c:1979

sk_common_release+0xaf/0x3f0 net/core/sock.c:3820

inet_release+0x1e0/0x260 net/ipv4/af_inet.c:437

inet6_release+0x6f/0xd0 net/ipv6/af_inet6.c:489

__sock_release net/socket.c:658 [inline]

sock_release+0xa0/0x210 net/socket.c:686

cleanup_bearer+0x42d/0x4c0 net/tipc/udp_media.c:819

process_one_work kernel/workqueue.c:3229 [inline]

process_scheduled_works+0xcaf/0x1c90 kernel/workqueue.c:3310

worker_thread+0xf6c/0x1510 kernel/workqueue.c:3391

kthread+0x531/0x6b0 kernel/kthread.c:389

ret_from_fork+0x60/0x80 arch/x86/kernel/process.c:147

ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244

Uninit was created at:

slab_free_hook mm/slub.c:2269 [inline]

slab_free mm/slub.c:4580 [inline]

kmem_cache_free+0x207/0xc40 mm/slub.c:4682

net_free net/core/net_namespace.c:454 [inline]

cleanup_net+0x16f2/0x19d0 net/core/net_namespace.c:647

process_one_work kernel/workqueue.c:3229 [inline]

process_scheduled_works+0xcaf/0x1c90 kernel/workqueue.c:3310

worker_thread+0xf6c/0x1510 kernel/workqueue.c:3391

kthread+0x531/0x6b0 kernel/kthread.c:389

ret_from_fork+0x60/0x80 arch/x86/kernel/process.c:147

ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244

CPU: 0 UID: 0 PID: 54 Comm: kworker/0:2 Not tainted 6.12.0-rc1-00131-gf66ebf37d69c #7 91723d6f74857f70725e1583cba3cf4adc716cfa

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014

Workqueue: events cleanup_bearer