mailbox: qcom-cpucp: fix PREEMPT_RT self-deadlock in IRQ handler
qcom_cpucp_mbox_irq_fn() calls mbox_chan_received_data() while holding
chan->lock. Under PREEMPT_RT, spin_lock_irqsave() is converted to an
rt_spinlock (rtmutex-based), which tracks ownership and can sleep.
The callback chain triggered by mbox_chan_received_data() eventually
reaches mailbox_clear_channel() -> mbox_send_message() -> add_to_rbuf(),
which attempts to re-acquire the same chan->lock. Since rtmutex detects
the re-entrant lock attempt by the same owner, the thread blocks waiting
for a lock it already holds, causing a permanent deadlock.
This deadlock manifests as 'irq/N-apss_cpucp_mbox' stuck in D state
with the following call trace:
rt_spin_lock -> mbox_send_message -> mailbox_clear_channel ->
scmi_rx_callback -> mbox_chan_received_data [<- held chan->lock here]
Fix by saving chan->cl locally and clearing the HW interrupt register
inside the lock, then invoking mbox_chan_received_data() after releasing
the lock. This preserves the mutual exclusion for chan->cl access while
avoiding the lock re-entrancy that causes the PREEMPT_RT deadlock.
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
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| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No vendor fix or workaround currently provided.
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Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: mailbox: qcom-cpucp: fix PREEMPT_RT self-deadlock in IRQ handler qcom_cpucp_mbox_irq_fn() calls mbox_chan_received_data() while holding chan->lock. Under PREEMPT_RT, spin_lock_irqsave() is converted to an rt_spinlock (rtmutex-based), which tracks ownership and can sleep. The callback chain triggered by mbox_chan_received_data() eventually reaches mailbox_clear_channel() -> mbox_send_message() -> add_to_rbuf(), which attempts to re-acquire the same chan->lock. Since rtmutex detects the re-entrant lock attempt by the same owner, the thread blocks waiting for a lock it already holds, causing a permanent deadlock. This deadlock manifests as 'irq/N-apss_cpucp_mbox' stuck in D state with the following call trace: rt_spin_lock -> mbox_send_message -> mailbox_clear_channel -> scmi_rx_callback -> mbox_chan_received_data [<- held chan->lock here] Fix by saving chan->cl locally and clearing the HW interrupt register inside the lock, then invoking mbox_chan_received_data() after releasing the lock. This preserves the mutual exclusion for chan->cl access while avoiding the lock re-entrancy that causes the PREEMPT_RT deadlock. | |
| Title | mailbox: qcom-cpucp: fix PREEMPT_RT self-deadlock in IRQ handler | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:07:13.672Z
Reserved: 2026-09-11T19:38:34.792Z
Link: CVE-2026-90193
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:14.030
Modified: 2026-09-17T17:17:14.030
Link: CVE-2026-90193
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.