CVE-2026-53331
UnknownSummary
In the Qualcomm slimbus driver (qcom-ngd-ctrl), a potential deadlock was found due to reversed locking order of tx_lock and ctrl->lock. During SSR/PDR down notification, tx_lock is taken and then slim_report_absent() tries to acquire ctrl->lock, causing a lock inversion and possible deadlock.
Risk Assessment
The deadlock may cause system hang or slimbus driver failure, affecting devices using this bus (e.g., audio, sensors). A local attacker could exploit this to cause a denial of service (DoS).
Recommendation
Immediately update the Linux kernel to a version containing the fix that removes the tx_lock acquisition in qcom_slim_ngd_ssr_pdr_notify(). Monitor your distribution for the patched release.
Original NVD description (English source)
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.