Vulnerabilities
- CVSS
- 5.5 Medium
- Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H- EPSS
- 0.13%
- Risk score
- 1.8
- Published
- 2026-07-01
- Status
- Analyzed
In the Linux kernel, the following vulnerability has been resolved:
slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock
During the SSR/PDR down notification the tx_lock is taken with the
intent to provide synchronization with active DMA transfers.
But during this period qcom_slim_ngd_down() is invoked, which ends up in
slim_report_absent(), which takes the slim_controller lock. In multiple
other codepaths these two locks are taken in the opposite order (i.e.
slim_controller then tx_lock).
The result is a lockdep splat, and a possible deadlock:
rprocctl/449 is trying to acquire lock:
ffff00009793e620 (&ctrl->lock){+.+.}-{4:4}, at: slim_report_absent (drivers/slimbus/core.c:322) slimbus
but task is already holding lock:
ffff00009793fb50 (&ctrl->tx_lock){+.+.}-{4:4}, at: qcom_slim_ngd_ssr_pdr_notify (drivers/slimbus/qcom-ngd-ctrl.c:1475) slim_qcom_ngd_ctrl
which lock already depends on the new lock.
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&ctrl->tx_lock);
lock(&ctrl->lock);
lock(&ctrl->tx_lock);
lock(&ctrl->lock);
The assumption is that the comment refers to the desire to not call
qcom_slim_ngd_exit_dma() while we have an ongoing DMA TX transaction.
But any such transaction is initiated and completed within a single
qcom_slim_ngd_xfer_msg().
Prior to calling qcom_slim_ngd_exit_dma() the slim_controller is torn
down, all child devices are notified that the slimbus is gone and the
child devices are removed.
Stop taking the tx_lock in qcom_slim_ngd_ssr_pdr_notify() to avoid the
deadlock.
Coverage 2
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Advisories and references