Hi,
There are 3 points about this bug:
1)
The onmax_destroy() destroyed the onmax var, casusing a double-free error
flagged by KASAN.
This is tested via "./ftracetest test.d/trigger/inter-event/trigger-onmatch-onmax-action-hist.tc".
==================================================================
BUG: KASAN: use-after-free in destroy_hist_field+0x1c2/0x200
Read of size 8 at addr ffff88800a4ad100 by task ftracetest/4731
CPU: 0 PID: 4731 Comm: ftracetest Kdump: loaded Tainted: GE 4.19.90-89 #77
Source Version: Unknown
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0
Call Trace:
dump_stack+0xcb/0x10b
print_address_description.cold+0x54/0x249
kasan_report_error.cold+0x63/0xab
? destroy_hist_field+0x1c2/0x200
? hist_trigger_elt_data_alloc+0x5a0/0x5a0
__asan_report_load8_noabort+0x8d/0xa0
? destroy_hist_field+0x1c2/0x200
destroy_hist_field+0x1c2/0x200
onmax_destroy+0x72/0x1e0
? hist_trigger_elt_data_alloc+0x5a0/0x5a0
destroy_hist_data+0x236/0xa40
event_hist_trigger_free+0x212/0x2f0
? update_cond_flag+0x128/0x170
? event_hist_trigger_func+0x2880/0x2880
hist_unregister_trigger+0x2f2/0x4f0
event_hist_trigger_func+0x168c/0x2880
? tracing_map_cmp_u64+0xa0/0xa0
? onmatch_create.constprop.0+0xf50/0xf50
? __mutex_lock_slowpath+0x10/0x10
event_trigger_write+0x2f4/0x490
? trigger_start+0x180/0x180
? __fget_light+0x369/0x5d0
? count_memcg_event_mm+0x104/0x2b0
? trigger_start+0x180/0x180
__vfs_write+0x81/0x100
vfs_write+0x1e1/0x540
ksys_write+0x12a/0x290
? __ia32_sys_read+0xb0/0xb0
? __close_fd+0x1d3/0x280
do_syscall_64+0xe3/0x2d0
entry_SYSCALL_64_after_hwframe+0x5c/0xc1
RIP: 0033:0x7fd7f4c44e04
Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00
48 8d 05 39 34 0c 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00
f0 ff ff 77 54 f3 c3 66 90 41 54 55 49 89 d4 53 48 89 f5
RSP: 002b:00007fff10370df8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000000010f RCX: 00007fd7f4c44e04
RDX: 000000000000010f RSI: 000055fa765df650 RDI: 0000000000000001
RBP: 000055fa765df650 R08: 000000000000000a R09: 0000000000000000
R10: 000000000000000a R11: 0000000000000246 R12: 00007fd7f4d035c0
R13: 000000000000010f R14: 00007fd7f4d037c0 R15: 000000000000010f
==================================================================
2)
So remove the onmax_destroy() destroy_hist_field() call for that var.
just like this demo patch:
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 7dcb96305e56..58b8a2575b8c 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -3489,7 +3488,6 @@ static void onmax_destroy(struct action_data *data)
unsigned int i;
destroy_hist_field(data->onmax.max_var, 0);
- destroy_hist_field(data->onmax.var, 0);
kfree(data->onmax.var_str);
kfree(data->onmax.fn_name);
--
3)
And I found it has been fixed by upstream commit ff9d31d0d466.
So I am backporting these patches to linux-4.19.y.
Masami Hiramatsu (4):
tracing: Simplify creation and deletion of synthetic events
tracing: Add unified dynamic event framework
tracing: Use dyn_event framework for synthetic events
tracing: Remove unneeded synth_event_mutex
Steven Rostedt (VMware) (5):
tracing: Consolidate trace_add/remove_event_call back to the nolock
functions
string.h: Add str_has_prefix() helper function
tracing: Use str_has_prefix() helper for histogram code
tracing: Use str_has_prefix() instead of using fixed sizes
tracing: Have the historgram use the result of str_has_prefix() for
len of prefix
Tom Zanussi (4):
tracing: Refactor hist trigger action code
tracing: Split up onmatch action data
tracing: Generalize hist trigger onmax and save action
tracing: Remove unnecessary var_ref destroy in track_data_destroy()
include/linux/string.h | 20 +
include/linux/trace_events.h | 2 -
kernel/trace/Kconfig | 4 +
kernel/trace/Makefile | 1 +
kernel/trace/trace.c | 26 +-
kernel/trace/trace_dynevent.c | 210 ++++++
kernel/trace/trace_dynevent.h | 119 ++++
kernel/trace/trace_events.c | 32 +-
kernel/trace/trace_events_hist.c | 1048 ++++++++++++++++++------------
kernel/trace/trace_probe.c | 2 +-
kernel/trace/trace_stack.c | 2 +-
11 files changed, 1008 insertions(+), 458 deletions(-)
create mode 100644 kernel/trace/trace_dynevent.c
create mode 100644 kernel/trace/trace_dynevent.h
--
2.34.1
