In the Linux kernel, the following vulnerability has been resolved: drivers: perf: Do not broadcast to other cpus when starting a counter This command: $ perf record -e cycles:k -e instructions:k -c 10000 -m 64M dd if=/dev/zero of=/dev/null count=1000 gives rise to this kernel warning: [ 444.364395] WARNING: CPU: 0 PID: 104 at kernel/smp.c:775 smp_call_function_many_cond+0x42c/0x436 [ 444.364515] Modules linked in: [ 444.364657] CPU: 0 PID: 104 Comm: perf-exec Not tainted 6.6.0-rc6-00051-g391df82e8ec3-dirty #73 [ 444.364771] Hardware name: riscv-virtio,qemu (DT) [ 444.364868] epc : smp_call_function_many_cond+0x42c/0x436 [ 444.364917] ra : on_each_cpu_cond_mask+0x20/0x32 [ 444.364948] epc : ffffffff8009f9e0 ra : ffffffff8009fa5a sp : ff20000000003800 [ 444.364966] gp : ffffffff81500aa0 tp : ff60000002b83000 t0 : ff200000000038c0 [ 444.364982] t1 : ffffffff815021f0 t2 : 000000000000001f s0 : ff200000000038b0 [ 444.364998] s1 : ff60000002c54d98 a0 : ff60000002a73940 a1 : 0000000000000000 [ 444.365013] a2 : 0000000000000000 a3 : 0000000000000003 a4 : 0000000000000100 [ 444.365029] a5 : 0000000000010100 a6 : 0000000000f00000 a7 : 0000000000000000 [ 444.365044] s2 : 0000000000000000 s3 : ffffffffffffffff s4 : ff60000002c54d98 [ 444.365060] s5 : ffffffff81539610 s6 : ffffffff80c20c48 s7 : 0000000000000000 [ 444.365075] s8 : 0000000000000000 s9 : 0000000000000001 s10: 0000000000000001 [ 444.365090] s11: ffffffff80099394 t3 : 0000000000000003 t4 : 00000000eac0c6e6 [ 444.365104] t5 : 0000000400000000 t6 : ff60000002e010d0 [ 444.365120] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003 [ 444.365226] [<ffffffff8009f9e0>] smp_call_function_many_cond+0x42c/0x436 [ 444.365295] [<ffffffff8009fa5a>] on_each_cpu_cond_mask+0x20/0x32 [ 444.365311] [<ffffffff806e90dc>] pmu_sbi_ctr_start+0x7a/0xaa [ 444.365327] [<ffffffff806e880c>] riscv_pmu_start+0x48/0x66 [ 444.365339] [<ffffffff8012111a>] perf_adjust_freq_unthr_context+0x196/0x1ac [ 444.365356] [<ffffffff801237aa>] perf_event_task_tick+0x78/0x8c [ 444.365368] [<ffffffff8003faf4>] scheduler_tick+0xe6/0x25e [ 444.365383] [<ffffffff8008a042>] update_process_times+0x80/0x96 [ 444.365398] [<ffffffff800991ec>] tick_sched_handle+0x26/0x52 [ 444.365410] [<ffffffff800993e4>] tick_sched_timer+0x50/0x98 [ 444.365422] [<ffffffff8008a6aa>] __hrtimer_run_queues+0x126/0x18a [ 444.365433] [<ffffffff8008b350>] hrtimer_interrupt+0xce/0x1da [ 444.365444] [<ffffffff806cdc60>] riscv_timer_interrupt+0x30/0x3a [ 444.365457] [<ffffffff8006afa6>] handle_percpu_devid_irq+0x80/0x114 [ 444.365470] [<ffffffff80065b82>] generic_handle_domain_irq+0x1c/0x2a [ 444.365483] [<ffffffff8045faec>] riscv_intc_irq+0x2e/0x46 [ 444.365497] [<ffffffff808a9c62>] handle_riscv_irq+0x4a/0x74 [ 444.365521] [<ffffffff808aa760>] do_irq+0x7c/0x7e [ 444.365796] ---[ end trace 0000000000000000 ]--- That's because the fix in commit 3fec323339a4 ("drivers: perf: Fix panic in riscv SBI mmap support") was wrong since there is no need to broadcast to other cpus when starting a counter, that's only needed in mmap when the counters could have already been started on other cpus, so simply remove this broadcast.
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