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CVE Record

CVE-2022-50116: tty: n_gsm: fix deadlock and link starvation in outgoing data path

In the Linux kernel, the following vulnerability has been resolved: tty: n_gsm: fix deadlock and link starvation in outgoing data path The current implementation queues up new control and user packets as needed and processes this queue down to the ldisc in the same code path. That means that the upper and the lower layer are hard coupled in the code. Due to this deadlocks can happen as seen below while transmitting data, especially during ldisc congestion. Furthermore, the data channels starve the control channel on high transmission load on the ldisc. Introduce an additional control channel data queue to prevent timeouts and link hangups during ldisc congestion. This is being processed before the user channel data queue in gsm_data_kick(), i.e. with the highest priority. Put the queue to ldisc data path into a workqueue and trigger it whenever new data has been put into the transmission queue. Change gsm_dlci_data_sweep() accordingly to fill up the transmission queue until TX_THRESH_HI. This solves the locking issue, keeps latency low and provides good performance on high data load. Note that now all packets from a DLCI are removed from the internal queue if the associated DLCI was closed. This ensures that no data is sent by the introduced write task to an already closed DLCI. BUG: spinlock recursion on CPU#0, test_v24_loop/124 lock: serial8250_ports+0x3a8/0x7500, .magic: dead4ead, .owner: test_v24_loop/124, .owner_cpu: 0 CPU: 0 PID: 124 Comm: test_v24_loop Tainted: G O 5.18.0-rc2 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x34/0x44 do_raw_spin_lock+0x76/0xa0 _raw_spin_lock_irqsave+0x72/0x80 uart_write_room+0x3b/0xc0 gsm_data_kick+0x14b/0x240 [n_gsm] gsmld_write_wakeup+0x35/0x70 [n_gsm] tty_wakeup+0x53/0x60 tty_port_default_wakeup+0x1b/0x30 serial8250_tx_chars+0x12f/0x220 serial8250_handle_irq.part.0+0xfe/0x150 serial8250_default_handle_irq+0x48/0x80 serial8250_interrupt+0x56/0xa0 __handle_irq_event_percpu+0x78/0x1f0 handle_irq_event+0x34/0x70 handle_fasteoi_irq+0x90/0x1e0 __common_interrupt+0x69/0x100 common_interrupt+0x48/0xc0 asm_common_interrupt+0x1e/0x40 RIP: 0010:__do_softirq+0x83/0x34e Code: 2a 0a ff 0f b7 ed c7 44 24 10 0a 00 00 00 48 c7 c7 51 2a 64 82 e8 2d e2 d5 ff 65 66 c7 05 83 af 1e 7e 00 00 fb b8 ff ff ff ff <49> c7 c2 40 61 80 82 0f bc c5 41 89 c4 41 83 c4 01 0f 84 e6 00 00 RSP: 0018:ffffc90000003f98 EFLAGS: 00000286 RAX: 00000000ffffffff RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff82642a51 RDI: ffffffff825bb5e7 RBP: 0000000000000200 R08: 00000008de3271a8 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000030 R14: 0000000000000000 R15: 0000000000000000 ? __do_softirq+0x73/0x34e irq_exit_rcu+0xb5/0x100 common_interrupt+0xa4/0xc0 </IRQ> <TASK> asm_common_interrupt+0x1e/0x40 RIP: 0010:_raw_spin_unlock_irqrestore+0x2e/0x50 Code: 00 55 48 89 fd 48 83 c7 18 53 48 89 f3 48 8b 74 24 10 e8 85 28 36 ff 48 89 ef e8 cd 58 36 ff 80 e7 02 74 01 fb bf 01 00 00 00 <e8> 3d 97 33 ff 65 8b 05 96 23 2b 7e 85 c0 74 03 5b 5d c3 0f 1f 44 RSP: 0018:ffffc9000020fd08 EFLAGS: 00000202 RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000000 RDX: 0000000000000004 RSI: ffffffff8257fd74 RDI: 0000000000000001 RBP: ffff8880057de3a0 R08: 00000008de233000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000100 R14: 0000000000000202 R15: ffff8880057df0b8 ? _raw_spin_unlock_irqrestore+0x23/0x50 gsmtty_write+0x65/0x80 [n_gsm] n_tty_write+0x33f/0x530 ? swake_up_all+0xe0/0xe0 file_tty_write.constprop.0+0x1b1/0x320 ? n_tty_flush_buffer+0xb0/0xb0 new_sync_write+0x10c/0x190 vfs_write+0x282/0x310 ksys_write+0x68/0xe0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f3e5e35c15c Code: 8b 7c 24 08 89 c5 e8 c5 ff ff ff 89 ef 89 44 24 ---truncated---

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects the n_gsm TTY data path. Under congested outgoing data handling, the kernel can deadlock or starve control traffic, causing timeouts or link hangups. The source bundle does not provide CVSS, confirmed exploitation, or broad business impact details.

Executive priority

Treat this as a targeted kernel reliability risk until vendor severity is clarified. Prioritize embedded, modem-connected, or telecom-adjacent Linux assets, while tracking normal kernel patch cycles for general infrastructure.

Technical view

The vulnerability is in Linux tty n_gsm outgoing transmission handling. User and control packets were processed in a tightly coupled path, allowing spinlock recursion during ldisc congestion and control-channel starvation under high load. The fix introduces prioritized control-channel queuing and workqueue-based transmission processing.

Likely exposure

Exposure is most relevant to Linux systems or embedded devices using the n_gsm line discipline. Generic Linux systems that do not use this path may have limited exposure. The source bundle does not define required privileges, attack surface, or distribution-specific affected packages.

Exploitation context

No active exploitation is supported by the provided sources, and KEV is false. The evidence shows a kernel deadlock observed in testing during data transmission and line discipline congestion, not a public exploit or remote attack scenario.

Researcher notes

The source bundle describes a resolved kernel concurrency flaw, but lacks CVSS, CWE, exploitability prerequisites, and distribution status. Analysis should stay focused on n_gsm usage, ldisc congestion behavior, and whether local write paths can trigger service impact.

Mitigation direction

  • Check Linux vendor guidance for fixed kernels containing the referenced stable commits.
  • Prioritize updates for systems using n_gsm or modem multiplexing functionality.
  • Apply distribution kernel updates rather than manually cherry-picking unless vendor process requires it.
  • Monitor kernel and distribution advisories for severity or prerequisite clarification.

Validation and detection

  • Inventory Linux kernel versions across affected fleets and embedded devices.
  • Identify systems loading or relying on the n_gsm TTY line discipline.
  • Compare installed kernel builds against vendor advisories and referenced stable fixes.
  • Review operational incidents for n_gsm timeouts, link hangups, or related deadlock symptoms.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2022-50116 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
5Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxe1eaea46bb4020b38a141b84f88565d4603f8dd0, e1eaea46bb4020b38a141b84f88565d4603f8dd0, e1eaea46bb4020b38a141b84f88565d4603f8dd0, e1eaea46bb4020b38a141b84f88565d4603f8dd0unaffected
LinuxLinux2.6.35, 0, 5.15.209, 5.18.18, 5.19.2, 6.0affected
Weakness

CWE details

No CWE listed

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