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.

kernel.org https://git.kernel.org/stable/c/61e3d993c8bd3e80f8f1363ed5e04f88ab531b72 [No types assigned]

kernel.org https://git.kernel.org/stable/c/85be1a73fd298ed3fd060dfce97caef5f9928c57 [No types assigned]