In the Linux kernel, the following vulnerability has been resolved:
mptcp: use the workqueue to destroy unaccepted sockets
Christoph reported a UaF at token lookup time after having refactored the passive socket initialization part:
BUG: KASAN: use-after-free in __token_bucket_busy+0x253/0x260 Read of size 4 at addr ffff88810698d5b0 by task syz-executor653/3198
CPU: 1 PID: 3198 Comm: syz-executor653 Not tainted 6.2.0-rc59af4eaa31c1f6c00c8f1e448ed99a45c66340dd5 #6 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x6e/0x91 print_report+0x16a/0x46f kasan_report+0xad/0x130 __token_bucket_busy+0x253/0x260 mptcp_token_new_connect+0x13d/0x490 mptcp_connect+0x4ed/0x860 __inet_stream_connect+0x80e/0xd90 tcp_sendmsg_fastopen+0x3ce/0x710 mptcp_sendmsg+0xff1/0x1a20 inet_sendmsg+0x11d/0x140 __sys_sendto+0x405/0x490 __x64_sys_sendto+0xdc/0x1b0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc
We need to properly clean-up all the paired MPTCP-level resources and be sure to release the msk last, even when the unaccepted subflow is destroyed by the TCP internals via inet_child_forget().
We can re-use the existing MPTCP_WORK_CLOSE_SUBFLOW infra, explicitly checking that for the critical scenario: the closed subflow is the MPC one, the msk is not accepted and eventually going through full cleanup.
With such change, __mptcp_destroy_sock() is always called on msk sockets, even on accepted ones. We don't need anymore to transiently drop one sk reference at msk clone time.
Please note this commit depends on the parent one:
mptcp: refactor passive socket initialization
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade bpftool-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade python3-perf-debuginfoUpgrade kernel-toolsUpgrade perf-debuginfoUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-develUpgrade python3-perfUpgrade kernel-headersUpgrade kernel-libbpfUpgrade kernel-tools-debuginfoUpgrade kernelUpgrade kernel-debuginfoUpgrade kernel-libbpf-develUpgrade kernel-livepatch-6.1.23-36.46Upgrade bpftoolUpgrade perfUpgrade kernel-tools-develUpgrade kernel-libbpf-static | Aug 5, 2025 | May 2, 2025 |
| Debian | — | Upgrade linux | May 5, 2025 | May 2, 2025 |
| Redhat_linux | — | No solution existsUpgrade kernel | Jul 9, 2025 | May 2, 2025 |
| Ubuntu | — | No solution exists | Jun 26, 2025 | May 2, 2025 |
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