From: "Steven Rostedt (VMware)" <[email protected]>
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).
Cc: [email protected]
Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to synthetic events")
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
---
kernel/trace/trace_synth.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_synth.h b/kernel/trace/trace_synth.h
index 6e146b959dcd..4007fe95cf42 100644
--- 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 {
--
2.31.1
Hi Steve,
On Wed, 2021-07-21 at 19:10 -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <[email protected]>
>
> 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,pr
> ev_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).
>
> Cc: [email protected]
> Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to
> synthetic events")
> Signed-off-by: Steven Rostedt (VMware) <[email protected]>
> ---
> kernel/trace/trace_synth.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_synth.h b/kernel/trace/trace_synth.h
> index 6e146b959dcd..4007fe95cf42 100644
> --- 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 {
Good catch, thanks,
Reviewed-by: Tom Zanussi <[email protected]>