| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47242: mptcp: fix soft lookup in subflow_error_report() |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| mptcp: fix soft lookup in subflow_error_report() |
| |
| Maxim reported a soft lookup in subflow_error_report(): |
| |
| watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:0] |
| RIP: 0010:native_queued_spin_lock_slowpath |
| RSP: 0018:ffffa859c0003bc0 EFLAGS: 00000202 |
| RAX: 0000000000000101 RBX: 0000000000000001 RCX: 0000000000000000 |
| RDX: ffff9195c2772d88 RSI: 0000000000000000 RDI: ffff9195c2772d88 |
| RBP: ffff9195c2772d00 R08: 00000000000067b0 R09: c6e31da9eb1e44f4 |
| R10: ffff9195ef379700 R11: ffff9195edb50710 R12: ffff9195c2772d88 |
| R13: ffff9195f500e3d0 R14: ffff9195ef379700 R15: ffff9195ef379700 |
| FS: 0000000000000000(0000) GS:ffff91961f400000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 000000c000407000 CR3: 0000000002988000 CR4: 00000000000006f0 |
| Call Trace: |
| <IRQ> |
| _raw_spin_lock_bh |
| subflow_error_report |
| mptcp_subflow_data_available |
| __mptcp_move_skbs_from_subflow |
| mptcp_data_ready |
| tcp_data_queue |
| tcp_rcv_established |
| tcp_v4_do_rcv |
| tcp_v4_rcv |
| ip_protocol_deliver_rcu |
| ip_local_deliver_finish |
| __netif_receive_skb_one_core |
| netif_receive_skb |
| rtl8139_poll 8139too |
| __napi_poll |
| net_rx_action |
| __do_softirq |
| __irq_exit_rcu |
| common_interrupt |
| </IRQ> |
| |
| The calling function - mptcp_subflow_data_available() - can be invoked |
| from different contexts: |
| - plain ssk socket lock |
| - ssk socket lock + mptcp_data_lock |
| - ssk socket lock + mptcp_data_lock + msk socket lock. |
| |
| Since subflow_error_report() tries to acquire the mptcp_data_lock, the |
| latter two call chains will cause soft lookup. |
| |
| This change addresses the issue moving the error reporting call to |
| outer functions, where the held locks list is known and the we can |
| acquire only the needed one. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47242 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.12 with commit 15cc10453398c22f78f6c2b897119ecce5e5dd89 and fixed in 5.12.13 with commit 27ef25c72373222aaa5fe7b5cd890ae9cfb89a8d |
| Issue introduced in 5.12 with commit 15cc10453398c22f78f6c2b897119ecce5e5dd89 and fixed in 5.13 with commit 499ada5073361c631f2a3c4a8aed44d53b6f82ec |
| Issue introduced in 5.11.12 with commit c8ad65cb5051498b8a58be40499db9e930f0092e |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47242 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| net/mptcp/protocol.c |
| net/mptcp/subflow.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/27ef25c72373222aaa5fe7b5cd890ae9cfb89a8d |
| https://git.kernel.org/stable/c/499ada5073361c631f2a3c4a8aed44d53b6f82ec |
