CVE-2026-80997
massCellular TX queue stall in Linux kernel Qualcomm IPA driver after runtime resume
The Qualcomm IPA (IP accelerator) modem driver in the Linux kernel has a runtime power-management race in which the wake work scheduled from the runtime-resume callback can run while the device is still RPM_RESUMING; the wake is consumed too early, pm_runtime_get() returns -EINPROGRESS with no future wake arranged, and the transmit queue is stopped forever, with packets piling up in the qdisc while the device runtime-suspends and RX also goes dead. The trigger is a single transmit racing an in-flight modem resume, and because the netdev registers no ndo_tx_timeout, the watchdog never fires; an accelerated reproducer (5 ms autosuspend, ~20 packets/s) stalled an unpatched kernel three times in 230 s / 4,380 packets, while the patched kernel ran 3,601 s / 70,298 packets without a stall. The impact is denial of service only (CVSS 3.1 7.5, availability:high, no confidentiality or integrity impact) — the cellular data path goes permanently deaf within hours, as observed on a Fairphone 6 (SM7635) — and an attacker able to influence transmit timing against the modem's autosuspend cycle could in principle trigger it remotely. Anyone running an affected kernel on Qualcomm Snapdragon hardware using the IPA driver for cellular data is exposed; no public proof of concept is known and no exploitation has been reported.
What to do: Update to a kernel that includes the upstream IPA fix, in which the wake work waits for resume completion via pm_runtime_get_sync() and wakes the queue even if resume fails, and obtain it through your distro, OEM, or ROM update channel. On an already-stalled device, toggling airplane mode or rebooting restores cellular connectivity. Because no tx timeout is logged, monitor fleets of Qualcomm-based cellular devices for mobile-data interfaces going silent after idle periods — look for rising qdisc backlog with zero TX/RX progress rather than watchdog events.
| Linux kernel (Qualcomm IPA network driver) | Kernel releases from the commit that removed the IPA STARTED power flag (which made a single transmit during an in-flight resume sufficient to strand the queue) |
| Qualcomm Snapdragon SoCs with integrated modems using the IPA driver | — |
| Fairphone 6 smartphone | SM7635-based units running unpatched kernels (device where the stall was observed) |
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
In the Linux kernel, the following vulnerability has been resolved: net: ipa: fix stalled modem TX queue after runtime resume ipa_start_xmit() unconditionally stops the TX queue before calling pm_runtime_get(), relying on the wake scheduled by runtime resume (ipa_modem_wake_queue_work()) to restart it once power is ACTIVE. But that work is queued from within the runtime resume callback, before the device's power state reaches RPM_ACTIVE, so it can run while the device is still RPM_RESUMING. The wake is then consumed too early: the transmit it restarts stops the queue again, pm_runtime_get() returns -EINPROGRESS without arranging any future wake (deferred_resume exists only for RPM_SUSPENDING), and after the resume completes nothing is left to wake the queue. Transmit stalls permanently: packets pile up in the qdisc behind the stopped queue, the device runtime-suspends, and since the netdev registers no ndo_tx_timeout the watchdog never fires. Observed on SM7635 (Fairphone 6) as the cellular data path going permanently deaf within hours, RX included, since nothing resumes the suspended endpoints. Close the window by making the wake work wait for the resume to complete (pm_runtime_get_sync()) before waking the queue. Every queue stop is then guaranteed a later wake that happens while power is ACTIVE; a transmit racing a new suspend/resume cycle re-schedules the work. If the device could not be resumed, wake the queue anyway so pending packets are dropped by the transmit path rather than stranded. The STARTED power flag used to narrow this window: a wake running before the transmit path's stop suppressed that stop, but only once, as the flag was cleared by the first stop it absorbed. Removing the flag made a single transmit during an in-flight resume sufficient to strand the queue, which is the form observed. With an accelerated reproducer (autosuspend delay shortened to 5 ms, ~20 packets/s of TX), an unpatched kernel stalled three times in 230 s / 4380 packets; with this patch the same test ran 3601 s / 70298 packets without a stall.
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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