In the Linux kernel, the following vulnerability has been resolved: drivers/perf: hisi: Don't migrate perf to the CPU going to teardown The driver needs to migrate the perf context if the current using CPU going to teardown. By the time calling the cpuhp::teardown() callback the cpu_online_mask() hasn't updated yet and still includes the CPU going to teardown. In current driver's implementation we may migrate the context to the teardown CPU and leads to the below calltrace: ... [ 368.104662][ T932] task:cpuhp/0 state:D stack: 0 pid: 15 ppid: 2 flags:0x00000008 [ 368.113699][ T932] Call trace: [ 368.116834][ T932] __switch_to+0x7c/0xbc [ 368.120924][ T932] __schedule+0x338/0x6f0 [ 368.125098][ T932] schedule+0x50/0xe0 [ 368.128926][ T932] schedule_preempt_disabled+0x18/0x24 [ 368.134229][ T932] __mutex_lock.constprop.0+0x1d4/0x5dc [ 368.139617][ T932] __mutex_lock_slowpath+0x1c/0x30 [ 368.144573][ T932] mutex_lock+0x50/0x60 [ 368.148579][ T932] perf_pmu_migrate_context+0x84/0x2b0 [ 368.153884][ T932] hisi_pcie_pmu_offline_cpu+0x90/0xe0 [hisi_pcie_pmu] [ 368.160579][ T932] cpuhp_invoke_callback+0x2a0/0x650 [ 368.165707][ T932] cpuhp_thread_fun+0xe4/0x190 [ 368.170316][ T932] smpboot_thread_fn+0x15c/0x1a0 [ 368.175099][ T932] kthread+0x108/0x13c [ 368.179012][ T932] ret_from_fork+0x10/0x18 ... Use function cpumask_any_but() to find one correct active cpu to fixes this issue.
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