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From:   Yang Jihong <yangjihong1@huawei.com>
To:     <rostedt@goodmis.org>, <peterz@infradead.org>, <mingo@redhat.com>,
        <acme@kernel.org>, <mark.rutland@arm.com>,
        <alexander.shishkin@linux.intel.com>, <jolsa@kernel.org>,
        <namhyung@kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-perf-users@vger.kernel.org>
CC:     <yangjihong1@huawei.com>
Subject: [PATCH v4] perf/core: Fix reentry problem in perf_output_read_group
Date:   Thu, 18 Aug 2022 10:21:21 +0800
Message-ID: <20220818022121.116939-1-yangjihong1@huawei.com>
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perf_output_read_group may respond to IPI request of other cores and invoke
__perf_install_in_context function. As a result, hwc configuration is modified.
causing inconsistency and unexpected consequences.

Syzkaller has reported a problem with this scenario:

Internal error: Oops - undefined instruction: 0 [#1] SMP
Modules linked in:
CPU: 1 PID: 15523 Comm: syz-executor.3 Not tainted 5.10.0 #6
Hardware name: linux,dummy-virt (DT)
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO BTYPE=--)
pc : read_pmevcntrn+0x1e4/0x1ec arch/arm64/kernel/perf_event.c:423
lr : read_pmevcntrn+0x1e4/0x1ec arch/arm64/kernel/perf_event.c:423
sp : ffffa000174d6ee0
x29: ffffa000174d6ee0 x28: ffffedbca6b17a40
x27: ffffa000174d7310 x26: ffff4b3ec102e398
x25: 00000000ffffffff x24: 00000000ffffffff
x23: ffff4b3ed8afb000 x22: ffff4b3ed8afb160
x21: ffff4b3ed8afb184 x20: ffffedbca46aa3e0
x19: ffffedbca2a524bc x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000
x15: 0000000020000100 x14: 0000000000000000
x13: 0000000000000000 x12: ffff8967db15f63d
x11: 1fffe967db15f63c x10: ffff8967db15f63c
x9 : ffffedbca2a5273c x8 : ffff4b3ed8afb1e7
x7 : 0000000000000001 x6 : ffff8967db15f63c
x5 : ffff4b3f08b89400 x4 : 0000000000000000
x3 : ffffedbca2a00000 x2 : ffffedbca4690000
x1 : ffff4b3f08b89400 x0 : 0000000000000000
Call trace:
 read_pmevcntrn+0x1e4/0x1ec arch/arm64/kernel/perf_event.c:423
 armv8pmu_read_evcntr arch/arm64/kernel/perf_event.c:467 [inline]
 armv8pmu_read_hw_counter arch/arm64/kernel/perf_event.c:475 [inline]
 armv8pmu_read_counter+0x10c/0x1f0 arch/arm64/kernel/perf_event.c:528
 armpmu_event_update+0x9c/0x1bc drivers/perf/arm_pmu.c:247
 armpmu_read+0x24/0x30 drivers/perf/arm_pmu.c:264
 perf_output_read_group+0x4cc/0x71c kernel/events/core.c:6806
 perf_output_read+0x78/0x1c4 kernel/events/core.c:6845
 perf_output_sample+0xafc/0x1000 kernel/events/core.c:6892
 __perf_event_output kernel/events/core.c:7273 [inline]
 perf_event_output_forward+0xd8/0x130 kernel/events/core.c:7287
 __perf_event_overflow+0xbc/0x20c kernel/events/core.c:8943
 perf_swevent_overflow kernel/events/core.c:9019 [inline]
 perf_swevent_event+0x274/0x2c0 kernel/events/core.c:9047
 do_perf_sw_event kernel/events/core.c:9160 [inline]
 ___perf_sw_event+0x150/0x1b4 kernel/events/core.c:9191
 __perf_sw_event+0x58/0x7c kernel/events/core.c:9203
 perf_sw_event include/linux/perf_event.h:1177 [inline]
 mm_account_fault mm/memory.c:4707 [inline]
 handle_mm_fault+0x364/0x3f0 mm/memory.c:4758
 __do_page_fault arch/arm64/mm/fault.c:438 [inline]
 do_page_fault+0x334/0x8f0 arch/arm64/mm/fault.c:537
 do_translation_fault+0x188/0x1e0 arch/arm64/mm/fault.c:619
 do_mem_abort+0x68/0x120 arch/arm64/mm/fault.c:743
 el1_abort+0xc0/0x150 arch/arm64/kernel/entry-common.c:119
 el1_sync_handler+0x118/0x150 arch/arm64/kernel/entry-common.c:202
 el1_sync+0x74/0x100 arch/arm64/kernel/entry.S:665
 __arch_clear_user+0x20/0xa0 arch/arm64/lib/clear_user.S:25
 read_iter_zero+0x90/0x16c drivers/char/mem.c:718
 call_read_iter include/linux/fs.h:1954 [inline]
 do_iter_readv_writev+0x394/0x414 fs/read_write.c:735
 do_iter_read+0x1b0/0x280 fs/read_write.c:798
 vfs_readv+0xf0/0x150 fs/read_write.c:918
 do_readv+0x108/0x270 fs/read_write.c:955
 __do_sys_readv fs/read_write.c:1046 [inline]
 __se_sys_readv fs/read_write.c:1043 [inline]
 __arm64_sys_readv+0x54/0x64 fs/read_write.c:1043
 __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
 el0_svc_common.constprop.0+0xf4/0x414 arch/arm64/kernel/syscall.c:155
 do_el0_svc+0x50/0x11c arch/arm64/kernel/syscall.c:217
 el0_svc+0x20/0x30 arch/arm64/kernel/entry-common.c:353
 el0_sync_handler+0xe4/0x1e0 arch/arm64/kernel/entry-common.c:369
 el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683
Code: 940c387b d53be813 17ffff9c 940c3878 (d53bebd3)
---[ end trace 6aab9f4b33ebf0aa ]---
----------------
Code disassembly (best guess):
   0:	940c387b 	bl	0x30e1ec
   4:	d53be813 	mrs	x19, pmevcntr0_el0
   8:	17ffff9c 	b	0xfffffffffffffe78
   c:	940c3878 	bl	0x30e1ec
* 10:	d53bebd3 	mrs	x19, pmevcntr30_el0 <-- trapping instruction

Interrupts are not disabled when perf_output_read_group reads PMU counter.
In this case, IPI request may be received from other cores.
As a result, PMU configuration is modified and an error occurs when
reading PMU counter:

                   CPU0                                         CPU1
                                                    __se_sys_perf_event_open
                                                      perf_install_in_context
perf_output_read_group                                  smp_call_function_single
  for_each_sibling_event(sub, leader) {                   generic_exec_single
    if ((sub != event) &&                                   remote_function
        (sub->state == PERF_EVENT_STATE_ACTIVE))                    |
<enter IPI handler: __perf_install_in_context>   <----RAISE IPI-----+
__perf_install_in_context
  ctx_resched
    event_sched_out
      armpmu_del
        ...
        hwc->idx = -1; // event->hwc.idx is set to -1
...
<exit IPI>
            sub->pmu->read(sub);
              armpmu_read
                armv8pmu_read_counter
                  armv8pmu_read_hw_counter
                    int idx = event->hw.idx; // idx = -1
                    u64 val = armv8pmu_read_evcntr(idx);
                      u32 counter = ARMV8_IDX_TO_COUNTER(idx); // invalid counter = 30
                      read_pmevcntrn(counter) // undefined instruction

Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
Changes since v3:
  - Modify commit message according to Peter's suggestion.

Changes since v2:
  - Update commit message.

Changes since v1:
  - Adapt patch to mainline branch to solve compilation problem.

 kernel/events/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2621fd24ad26..752a9079a807 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6895,6 +6895,13 @@ static void perf_output_read_group(struct perf_output_handle *handle,
 	u64 read_format = event->attr.read_format;
 	u64 values[6];
 	int n = 0;
+	unsigned long flags;
+
+	/*
+	 * Disabling interrupts avoids all counter scheduling
+	 * (context switches, timer based rotation and IPIs).
+	 */
+	local_irq_save(flags);
 
 	values[n++] = 1 + leader->nr_siblings;
 
@@ -6931,6 +6938,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
 
 		__output_copy(handle, values, n * sizeof(u64));
 	}
+
+	local_irq_restore(flags);
 }
 
 #define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\
-- 
2.30.GIT