{"id":"CVE-2026-90193","published":"2026-09-17T17:17:14.030","lastModified":"2026-09-17T17:17:14.030","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmailbox: qcom-cpucp: fix PREEMPT_RT self-deadlock in IRQ handler\n\nqcom_cpucp_mbox_irq_fn() calls mbox_chan_received_data() while holding\nchan->lock. Under PREEMPT_RT, spin_lock_irqsave() is converted to an\nrt_spinlock (rtmutex-based), which tracks ownership and can sleep.\n\nThe callback chain triggered by mbox_chan_received_data() eventually\nreaches mailbox_clear_channel() -> mbox_send_message() -> add_to_rbuf(),\nwhich attempts to re-acquire the same chan->lock. Since rtmutex detects\nthe re-entrant lock attempt by the same owner, the thread blocks waiting\nfor a lock it already holds, causing a permanent deadlock.\n\nThis deadlock manifests as 'irq/N-apss_cpucp_mbox' stuck in D state\nwith the following call trace:\n  rt_spin_lock -> mbox_send_message -> mailbox_clear_channel ->\n  scmi_rx_callback -> mbox_chan_received_data [<- held chan->lock here]\n\nFix by saving chan->cl locally and clearing the HW interrupt register\ninside the lock, then invoking mbox_chan_received_data() after releasing\nthe lock. This preserves the mutual exclusion for chan->cl access while\navoiding the lock re-entrancy that causes the PREEMPT_RT deadlock.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/3690aaa6d18f6775c3e7932fb8af8c5bf6a6b69c","tags":[]},{"url":"https://git.kernel.org/stable/c/8b8de6400c86937ed57d680d06d716e167b381de","tags":[]},{"url":"https://git.kernel.org/stable/c/aa482273f32117c3adeba9b1cc945e0b5d33722d","tags":[]},{"url":"https://git.kernel.org/stable/c/e40b3edeaf25cd09e9c88edb1ef99373ca37593b","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}