| From 3b13911a2fd0dd0146c9777a254840c5466cf120 Mon Sep 17 00:00:00 2001 |
| From: "Steven Rostedt (VMware)" <rostedt@goodmis.org> |
| Date: Wed, 21 Jul 2021 19:10:08 -0400 |
| Subject: tracing: Synthetic event field_pos is an index not a boolean |
| |
| From: Steven Rostedt (VMware) <rostedt@goodmis.org> |
| |
| commit 3b13911a2fd0dd0146c9777a254840c5466cf120 upstream. |
| |
| Performing the following: |
| |
| ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > synthetic_events |
| ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs' > events/sched/sched_waking/trigger |
| ># echo 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs-$__arg__1:onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,prev_comm)'\ |
| > events/sched/sched_switch/trigger |
| ># echo 1 > events/synthetic/enable |
| |
| Crashed the kernel: |
| |
| BUG: kernel NULL pointer dereference, address: 000000000000001b |
| #PF: supervisor read access in kernel mode |
| #PF: error_code(0x0000) - not-present page |
| PGD 0 P4D 0 |
| Oops: 0000 [#1] PREEMPT SMP |
| CPU: 7 PID: 0 Comm: swapper/7 Not tainted 5.13.0-rc5-test+ #104 |
| Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 |
| RIP: 0010:strlen+0x0/0x20 |
| Code: f6 82 80 2b 0b bc 20 74 11 0f b6 50 01 48 83 c0 01 f6 82 80 2b 0b bc |
| 20 75 ef c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <80> 3f 00 74 10 |
| 48 89 f8 48 83 c0 01 80 38 9 f8 c3 31 |
| RSP: 0018:ffffaa75000d79d0 EFLAGS: 00010046 |
| RAX: 0000000000000002 RBX: ffff9cdb55575270 RCX: 0000000000000000 |
| RDX: ffff9cdb58c7a320 RSI: ffffaa75000d7b40 RDI: 000000000000001b |
| RBP: ffffaa75000d7b40 R08: ffff9cdb40a4f010 R09: ffffaa75000d7ab8 |
| R10: ffff9cdb4398c700 R11: 0000000000000008 R12: ffff9cdb58c7a320 |
| R13: ffff9cdb55575270 R14: ffff9cdb58c7a000 R15: 0000000000000018 |
| FS: 0000000000000000(0000) GS:ffff9cdb5aa00000(0000) knlGS:0000000000000000 |
| CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 |
| CR2: 000000000000001b CR3: 00000000c0612006 CR4: 00000000001706e0 |
| Call Trace: |
| trace_event_raw_event_synth+0x90/0x1d0 |
| action_trace+0x5b/0x70 |
| event_hist_trigger+0x4bd/0x4e0 |
| ? cpumask_next_and+0x20/0x30 |
| ? update_sd_lb_stats.constprop.0+0xf6/0x840 |
| ? __lock_acquire.constprop.0+0x125/0x550 |
| ? find_held_lock+0x32/0x90 |
| ? sched_clock_cpu+0xe/0xd0 |
| ? lock_release+0x155/0x440 |
| ? update_load_avg+0x8c/0x6f0 |
| ? enqueue_entity+0x18a/0x920 |
| ? __rb_reserve_next+0xe5/0x460 |
| ? ring_buffer_lock_reserve+0x12a/0x3f0 |
| event_triggers_call+0x52/0xe0 |
| trace_event_buffer_commit+0x1ae/0x240 |
| trace_event_raw_event_sched_switch+0x114/0x170 |
| __traceiter_sched_switch+0x39/0x50 |
| __schedule+0x431/0xb00 |
| schedule_idle+0x28/0x40 |
| do_idle+0x198/0x2e0 |
| cpu_startup_entry+0x19/0x20 |
| secondary_startup_64_no_verify+0xc2/0xcb |
| |
| The reason is that the dynamic events array keeps track of the field |
| position of the fields array, via the field_pos variable in the |
| synth_field structure. Unfortunately, that field is a boolean for some |
| reason, which means any field_pos greater than 1 will be a bug (in this |
| case it was 2). |
| |
| Link: https://lkml.kernel.org/r/20210721191008.638bce34@oasis.local.home |
| |
| Cc: Masami Hiramatsu <mhiramat@kernel.org> |
| Cc: Namhyung Kim <namhyung@kernel.org> |
| Cc: Ingo Molnar <mingo@kernel.org> |
| Cc: Andrew Morton <akpm@linux-foundation.org> |
| Cc: stable@vger.kernel.org |
| Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to synthetic events") |
| Reviewed-by: Tom Zanussi <zanussi@kernel.org> |
| Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| kernel/trace/trace_synth.h | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/kernel/trace/trace_synth.h |
| +++ b/kernel/trace/trace_synth.h |
| @@ -14,10 +14,10 @@ struct synth_field { |
| char *name; |
| size_t size; |
| unsigned int offset; |
| + unsigned int field_pos; |
| bool is_signed; |
| bool is_string; |
| bool is_dynamic; |
| - bool field_pos; |
| }; |
| |
| struct synth_event { |