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3b13911a2f
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: bd82631d7c ("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>
41 lines
876 B
C
41 lines
876 B
C
// SPDX-License-Identifier: GPL-2.0
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#ifndef __TRACE_SYNTH_H
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#define __TRACE_SYNTH_H
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#include "trace_dynevent.h"
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#define SYNTH_SYSTEM "synthetic"
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#define SYNTH_FIELDS_MAX 32
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#define STR_VAR_LEN_MAX MAX_FILTER_STR_VAL /* must be multiple of sizeof(u64) */
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struct synth_field {
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char *type;
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char *name;
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size_t size;
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unsigned int offset;
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unsigned int field_pos;
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bool is_signed;
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bool is_string;
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bool is_dynamic;
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};
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struct synth_event {
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struct dyn_event devent;
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int ref;
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char *name;
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struct synth_field **fields;
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unsigned int n_fields;
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struct synth_field **dynamic_fields;
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unsigned int n_dynamic_fields;
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unsigned int n_u64;
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struct trace_event_class class;
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struct trace_event_call call;
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struct tracepoint *tp;
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struct module *mod;
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};
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extern struct synth_event *find_synth_event(const char *name);
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#endif /* __TRACE_SYNTH_H */
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