CVE-2023-53136

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

af_unix: fix struct pid leaks in OOB support

syzbot reported struct pid leak [1].

Issue is that queue_oob() calls maybe_add_creds() which potentially holds a reference on a pid.

But skb->destructor is not set (either directly or by calling unix_scm_to_skb())

This means that subsequent kfree_skb() or consume_skb() would leak this reference.

In this fix, I chose to fully support scm even for the OOB message.

[1] BUG: memory leak unreferenced object 0xffff8881053e7f80 (size 128): comm syz-executor242, pid 5066, jiffies 4294946079 (age 13.220s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. backtrace: [] alloc_pid+0x6a/0x560 kernel/pid.c:180 [] copy_process+0x169f/0x26c0 kernel/fork.c:2285 [] kernel_clone+0xf7/0x610 kernel/fork.c:2684 [] __do_sys_clone+0x7c/0xb0 kernel/fork.c:2825 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 [] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Affected Software

References

• https://git.kernel.org/stable/c/2aab4b96900272885bc157f8b236abf1cdc02e08
• https://git.kernel.org/stable/c/a59d6306263c38e5c0592ea4451ca26a0778c947
• https://git.kernel.org/stable/c/ac1968ac399205fda9ee3b18f7de7416cb3a5d0d
• https://git.kernel.org/stable/c/f3969427fb06a2c3cd6efd7faab63505cfa76e76