CVE-2024-36972

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> af_unix: Update unix_sk(sk)-&gt;oob_skb under sk_receive_queue lock.<br /> <br /> Billy Jheng Bing-Jhong reported a race between __unix_gc() and<br /> queue_oob().<br /> <br /> __unix_gc() tries to garbage-collect close()d inflight sockets,<br /> and then if the socket has MSG_OOB in unix_sk(sk)-&gt;oob_skb, GC<br /> will drop the reference and set NULL to it locklessly.<br /> <br /> However, the peer socket still can send MSG_OOB message and<br /> queue_oob() can update unix_sk(sk)-&gt;oob_skb concurrently, leading<br /> NULL pointer dereference. [0]<br /> <br /> To fix the issue, let&amp;#39;s update unix_sk(sk)-&gt;oob_skb under the<br /> sk_receive_queue&amp;#39;s lock and take it everywhere we touch oob_skb.<br /> <br /> Note that we defer kfree_skb() in manage_oob() to silence lockdep<br /> false-positive (See [1]).<br /> <br /> [0]:<br /> BUG: kernel NULL pointer dereference, address: 0000000000000008<br /> PF: supervisor write access in kernel mode<br /> PF: error_code(0x0002) - not-present page<br /> PGD 8000000009f5e067 P4D 8000000009f5e067 PUD 9f5d067 PMD 0<br /> Oops: 0002 [#1] PREEMPT SMP PTI<br /> CPU: 3 PID: 50 Comm: kworker/3:1 Not tainted 6.9.0-rc5-00191-gd091e579b864 #110<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014<br /> Workqueue: events delayed_fput<br /> RIP: 0010:skb_dequeue (./include/linux/skbuff.h:2386 ./include/linux/skbuff.h:2402 net/core/skbuff.c:3847)<br /> Code: 39 e3 74 3e 8b 43 10 48 89 ef 83 e8 01 89 43 10 49 8b 44 24 08 49 c7 44 24 08 00 00 00 00 49 8b 14 24 49 c7 04 24 00 00 00 00 89 42 08 48 89 10 e8 e7 c5 42 00 4c 89 e0 5b 5d 41 5c c3 cc cc<br /> RSP: 0018:ffffc900001bfd48 EFLAGS: 00000002<br /> RAX: 0000000000000000 RBX: ffff8880088f5ae8 RCX: 00000000361289f9<br /> RDX: 0000000000000000 RSI: 0000000000000206 RDI: ffff8880088f5b00<br /> RBP: ffff8880088f5b00 R08: 0000000000080000 R09: 0000000000000001<br /> R10: 0000000000000003 R11: 0000000000000001 R12: ffff8880056b6a00<br /> R13: ffff8880088f5280 R14: 0000000000000001 R15: ffff8880088f5a80<br /> FS: 0000000000000000(0000) GS:ffff88807dd80000(0000) knlGS:0000000000000000<br /> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> CR2: 0000000000000008 CR3: 0000000006314000 CR4: 00000000007506f0<br /> PKRU: 55555554<br /> Call Trace:<br /> <br /> unix_release_sock (net/unix/af_unix.c:654)<br /> unix_release (net/unix/af_unix.c:1050)<br /> __sock_release (net/socket.c:660)<br /> sock_close (net/socket.c:1423)<br /> __fput (fs/file_table.c:423)<br /> delayed_fput (fs/file_table.c:444 (discriminator 3))<br /> process_one_work (kernel/workqueue.c:3259)<br /> worker_thread (kernel/workqueue.c:3329 kernel/workqueue.c:3416)<br /> kthread (kernel/kthread.c:388)<br /> ret_from_fork (arch/x86/kernel/process.c:153)<br /> ret_from_fork_asm (arch/x86/entry/entry_64.S:257)<br /> <br /> Modules linked in:<br /> CR2: 0000000000000008