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UBSAN: shift-out-of-bounds in drivers/perf/arm_pmuv3.c:716:25 shift exponent -1 is negative UBSAN: shift-out-of-bounds in drivers/perf/arm_pmuv3.c:658:13 shift exponent -1 is negative This occurred because a perf_event could reach armv8pmu event with a negative idx, typically when a valid counter could not be allocated. This issue was observed when running KVM on Radxa's Orion6 platform. The issue was previously guarded indirectly by armv8pmu_event_is_chained(), which internally warned and returned false for idx < 0. But since the commit 29227d6ea157 ("arm64: perf: Clean up enable/disable calls"), this check was removed. To prevent undefined behavior, add an explicit guard to early return from armv8pmu event if hw.idx < 0, similar to handling in other PMU drivers. (e.g. intel_pmu_disable_event() on arch/x86/events/intel/core.c) $ ./syz-execprog -executor=./syz-executor -repeat=0 -sandbox=none \ -disable=binfmt_misc,cgroups,close_fds,devlink_pci,ieee802154,net_dev,net_reset,nic_vf,swap,sysctl,tun,usb,vhci,wifi \ -procs=8 perf.syz r0 = perf_event_open(&(0x7f0000000240)={ 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_config_ext }, 0x0, 0x0, 0xffffffffffffffff, 0x0) perf_event_open(&(0x7f0000000280)={ 0x0, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_config_ext }, 0x0, 0x0, r0, 0x0) perf_event_open(&(0x7f0000000540)={ 0x3, 0x80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4, @perf_bp={0x0, 0x2}, 0x20, 0x0, 0x0, 0x0, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x81 }, 0x0, 0x0, r0, 0x0) ------------[ cut here ]------------ UBSAN: shift-out-of-bounds in drivers/perf/arm_pmuv3.c:716:25 shift exponent -1 is negative CPU: 0 UID: 0 PID: 8405 Comm: syz.3.19 Tainted: G W 6.16.0-rc2-g5982a539cdce #3 PREEMPT Tainted: [W]=WARN Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8 05/13/2025 Call trace: show_stack+0x2c/0x3c (C) __dump_stack+0x30/0x40 dump_stack_lvl+0xd8/0x12c dump_stack+0x1c/0x28 ubsan_epilogue+0x14/0x48 __ubsan_handle_shift_out_of_bounds+0x2b0/0x34c armv8pmu_enable_event+0x3c4/0x4b0 armpmu_start+0xc4/0x118 perf_event_unthrottle_group+0x3a8/0x50c perf_adjust_freq_unthr_events+0x2f4/0x578 perf_adjust_freq_unthr_context+0x278/0x46c perf_event_task_tick+0x394/0x5b0 sched_tick+0x314/0x6cc update_process_times+0x374/0x4b0 tick_nohz_handler+0x334/0x480 __hrtimer_run_queues+0x3ec/0xb78 hrtimer_interrupt+0x2b8/0xb50 arch_timer_handler_virt+0x74/0x88 handle_percpu_devid_irq+0x174/0x308 generic_handle_domain_irq+0xe0/0x140 gic_handle_irq+0x6c/0x190 call_on_irq_stack+0x24/0x30 do_interrupt_handler+0xd4/0x138 el1_interrupt+0x34/0x54 el1h_64_irq_handler+0x18/0x24 el1h_64_irq+0x6c/0x70 generic_exec_single+0x2dc/0x304 (P) smp_call_function_single+0x308/0x530 perf_install_in_context+0x4a0/0x798 __arm64_sys_perf_event_open+0x184c/0x1d50 invoke_syscall+0x98/0x2b8 el0_svc_common+0x130/0x23c do_el0_svc+0x48/0x58 el0_svc+0x58/0x17c el0t_64_sync_handler+0x78/0x108 el0t_64_sync+0x198/0x19c ---[ end trace ]--- ------------[ cut here ]------------ UBSAN: shift-out-of-bounds in drivers/perf/arm_pmuv3.c:658:13 shift exponent -1 is negative CPU: 0 UID: 0 PID: 8006 Comm: syz.0.19 Not tainted 6.16.0-rc2-g5982a539cdce #3 PREEMPT Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8 05/13/2025 Call trace: show_stack+0x2c/0x3c (C) __dump_stack+0x30/0x40 dump_stack_lvl+0xd8/0x12c dump_stack+0x1c/0x28 ubsan_epilogue+0x14/0x48 __ubsan_handle_shift_out_of_bounds+0x2b0/0x34c armv8pmu_disable_event+0x228/0x2f8 armpmu_stop+0xa0/0x104 perf_event_throttle_group+0x354/0x4cc __perf_event_account_interrupt+0x26c/0x290 __perf_event_overflow+0xe8/0xd28 perf_event_overflow+0x38/0x4c armv8pmu_handle_irq+0x244/0x320 armpmu_dispatch_irq+0x6c/0x9c handle_percpu_devid_irq+0x174/0x308 generic_handle_domain_irq+0xe0/0x140 gic_handle_irq+0x6c/0x190 call_on_irq_stack+0x24/0x30 do_interrupt_handler+0xd4/0x138 el1_interrupt+0x34/0x54 el1h_64_irq_handler+0x18/0x24 el1h_64_irq+0x6c/0x70 generic_exec_single+0x2dc/0x304 (P) smp_call_function_single+0x308/0x530 perf_install_in_context+0x4a0/0x798 __arm64_sys_perf_event_open+0x184c/0x1d50 invoke_syscall+0x98/0x2b8 el0_svc_common+0x130/0x23c do_el0_svc+0x48/0x58 el0_svc+0x58/0x17c el0t_64_sync_handler+0x78/0x108 el0t_64_sync+0x198/0x19c ---[ end trace ]--- ------------[ cut here ]------------ UBSAN: shift-out-of-bounds in drivers/perf/arm_pmuv3.c:730:26 shift exponent -1 is negative CPU: 0 UID: 0 PID: 8006 Comm: syz.0.19 Not tainted 6.16.0-rc2-g5982a539cdce #3 PREEMPT Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8 05/13/2025 Call trace: show_stack+0x2c/0x3c (C) __dump_stack+0x30/0x40 dump_stack_lvl+0xd8/0x12c dump_stack+0x1c/0x28 ubsan_epilogue+0x14/0x48 __ubsan_handle_shift_out_of_bounds+0x2b0/0x34c armv8pmu_disable_event+0x298/0x2f8 armpmu_stop+0xa0/0x104 perf_event_throttle_group+0x354/0x4cc __perf_event_account_interrupt+0x26c/0x290 __perf_event_overflow+0xe8/0xd28 perf_event_overflow+0x38/0x4c armv8pmu_handle_irq+0x244/0x320 armpmu_dispatch_irq+0x6c/0x9c handle_percpu_devid_irq+0x174/0x308 generic_handle_domain_irq+0xe0/0x140 gic_handle_irq+0x6c/0x190 call_on_irq_stack+0x24/0x30 do_interrupt_handler+0xd4/0x138 el1_interrupt+0x34/0x54 el1h_64_irq_handler+0x18/0x24 el1h_64_irq+0x6c/0x70 generic_exec_single+0x2dc/0x304 (P) smp_call_function_single+0x308/0x530 perf_install_in_context+0x4a0/0x798 __arm64_sys_perf_event_open+0x184c/0x1d50 invoke_syscall+0x98/0x2b8 el0_svc_common+0x130/0x23c do_el0_svc+0x48/0x58 el0_svc+0x58/0x17c el0t_64_sync_handler+0x78/0x108 el0t_64_sync+0x198/0x19c ---[ end trace ]--- Fixes: 29227d6ea157 ("arm64: perf: Clean up enable/disable calls") Signed-off-by: Yunseong Kim Tested-by: Yunseong Kim Cc: Yeoreum Yun Cc: syzkaller@googlegroups.com --- drivers/perf/arm_pmuv3.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c index 3db9f4ed17e8..846d69643fd8 100644 --- a/drivers/perf/arm_pmuv3.c +++ b/drivers/perf/arm_pmuv3.c @@ -795,6 +795,9 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu) static void armv8pmu_enable_event(struct perf_event *event) { + if (unlikely(event->hw.idx < 0)) + return; + armv8pmu_write_event_type(event); armv8pmu_enable_event_irq(event); armv8pmu_enable_event_counter(event); @@ -802,6 +805,9 @@ static void armv8pmu_enable_event(struct perf_event *event) static void armv8pmu_disable_event(struct perf_event *event) { + if (unlikely(event->hw.idx < 0)) + return; + armv8pmu_disable_event_counter(event); armv8pmu_disable_event_irq(event); } -- 2.50.0