linux.git/kernel/trace/trace_fprobe.c, branch v6.18.21

tracing: tprobe-events: Fix to put tracepoint_user when disable the tprobe

2025-11-06T22:36:20+00:00

__unregister_trace_fprobe() checks tf->tuser to put it when removing
tprobe. However, disable_trace_fprobe() does not use it and only calls
unregister_fprobe(). Thus it forgets to disable tracepoint_user.

If the trace_fprobe has tuser, put it for unregistering the tracepoint
callbacks when disabling tprobe correctly.

Link: https://lore.kernel.org/all/176244794466.155515.3971904050506100243.stgit@devnote2/

Fixes: 2867495dea86 ("tracing: tprobe-events: Register tracepoint when enable tprobe event")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) 
Tested-by: Beau Belgrave 
Reviewed-by: Beau Belgrave

tracing: tprobe-events: Fix to register tracepoint correctly

2025-11-06T22:32:55+00:00

Since __tracepoint_user_init() calls tracepoint_user_register() without
initializing tuser->tpoint with given tracpoint, it does not register
tracepoint stub function as callback correctly, and tprobe does not work.

Initializing tuser->tpoint correctly before tracepoint_user_register()
so that it sets up tracepoint callback.

I confirmed below example works fine again.

echo "t sched_switch preempt prev_pid=prev->pid next_pid=next->pid" > /sys/kernel/tracing/dynamic_events
echo 1 > /sys/kernel/tracing/events/tracepoints/sched_switch/enable
cat /sys/kernel/tracing/trace_pipe

Link: https://lore.kernel.org/all/176244793514.155515.6466348656998627773.stgit@devnote2/

Fixes: 2867495dea86 ("tracing: tprobe-events: Register tracepoint when enable tprobe event")
Reported-by: Beau Belgrave 
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) 
Tested-by: Beau Belgrave 
Reviewed-by: Beau Belgrave

tracing: Fix race condition in kprobe initialization causing NULL pointer dereference

2025-10-01T23:05:01+00:00

There is a critical race condition in kprobe initialization that can lead to
NULL pointer dereference and kernel crash.

[1135630.084782] Unable to handle kernel paging request at virtual address 0000710a04630000
...
[1135630.260314] pstate: 404003c9 (nZcv DAIF +PAN -UAO)
[1135630.269239] pc : kprobe_perf_func+0x30/0x260
[1135630.277643] lr : kprobe_dispatcher+0x44/0x60
[1135630.286041] sp : ffffaeff4977fa40
[1135630.293441] x29: ffffaeff4977fa40 x28: ffffaf015340e400
[1135630.302837] x27: 0000000000000000 x26: 0000000000000000
[1135630.312257] x25: ffffaf029ed108a8 x24: ffffaf015340e528
[1135630.321705] x23: ffffaeff4977fc50 x22: ffffaeff4977fc50
[1135630.331154] x21: 0000000000000000 x20: ffffaeff4977fc50
[1135630.340586] x19: ffffaf015340e400 x18: 0000000000000000
[1135630.349985] x17: 0000000000000000 x16: 0000000000000000
[1135630.359285] x15: 0000000000000000 x14: 0000000000000000
[1135630.368445] x13: 0000000000000000 x12: 0000000000000000
[1135630.377473] x11: 0000000000000000 x10: 0000000000000000
[1135630.386411] x9 : 0000000000000000 x8 : 0000000000000000
[1135630.395252] x7 : 0000000000000000 x6 : 0000000000000000
[1135630.403963] x5 : 0000000000000000 x4 : 0000000000000000
[1135630.412545] x3 : 0000710a04630000 x2 : 0000000000000006
[1135630.421021] x1 : ffffaeff4977fc50 x0 : 0000710a04630000
[1135630.429410] Call trace:
[1135630.434828]  kprobe_perf_func+0x30/0x260
[1135630.441661]  kprobe_dispatcher+0x44/0x60
[1135630.448396]  aggr_pre_handler+0x70/0xc8
[1135630.454959]  kprobe_breakpoint_handler+0x140/0x1e0
[1135630.462435]  brk_handler+0xbc/0xd8
[1135630.468437]  do_debug_exception+0x84/0x138
[1135630.475074]  el1_dbg+0x18/0x8c
[1135630.480582]  security_file_permission+0x0/0xd0
[1135630.487426]  vfs_write+0x70/0x1c0
[1135630.493059]  ksys_write+0x5c/0xc8
[1135630.498638]  __arm64_sys_write+0x24/0x30
[1135630.504821]  el0_svc_common+0x78/0x130
[1135630.510838]  el0_svc_handler+0x38/0x78
[1135630.516834]  el0_svc+0x8/0x1b0

kernel/trace/trace_kprobe.c: 1308
0xffff3df8995039ec :     ldr     x21, [x24,#120]
include/linux/compiler.h: 294
0xffff3df8995039f0 :     ldr     x1, [x21,x0]

kernel/trace/trace_kprobe.c
1308: head = this_cpu_ptr(call->perf_events);
1309: if (hlist_empty(head))
1310: 	return 0;

crash> struct trace_event_call -o
struct trace_event_call {
  ...
  [120] struct hlist_head *perf_events;  //(call->perf_event)
  ...
}

crash> struct trace_event_call ffffaf015340e528
struct trace_event_call {
  ...
  perf_events = 0xffff0ad5fa89f088, //this value is correct, but x21 = 0
  ...
}

Race Condition Analysis:

The race occurs between kprobe activation and perf_events initialization:

  CPU0                                    CPU1
  ====                                    ====
  perf_kprobe_init
    perf_trace_event_init
      tp_event->perf_events = list;(1)
      tp_event->class->reg (2)← KPROBE ACTIVE
                                          Debug exception triggers
                                          ...
                                          kprobe_dispatcher
                                            kprobe_perf_func (tk->tp.flags & TP_FLAG_PROFILE)
                                              head = this_cpu_ptr(call->perf_events)(3)
                                              (perf_events is still NULL)

Problem:
1. CPU0 executes (1) assigning tp_event->perf_events = list
2. CPU0 executes (2) enabling kprobe functionality via class->reg()
3. CPU1 triggers and reaches kprobe_dispatcher
4. CPU1 checks TP_FLAG_PROFILE - condition passes (step 2 completed)
5. CPU1 calls kprobe_perf_func() and crashes at (3) because
   call->perf_events is still NULL

CPU1 sees that kprobe functionality is enabled but does not see that
perf_events has been assigned.

Add pairing read and write memory barriers to guarantee that if CPU1
sees that kprobe functionality is enabled, it must also see that
perf_events has been assigned.

Link: https://lore.kernel.org/all/20251001022025.44626-1-chenyuan_fl@163.com/

Fixes: 50d780560785 ("tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use")
Cc: stable@vger.kernel.org
Signed-off-by: Yuan Chen 
Signed-off-by: Masami Hiramatsu (Google)

tracing: trace_fprobe: Fix typo of the semicolon

2025-07-28T23:37:52+00:00

Fix a typo that uses ',' instead of ';' for line delimiter.

Link: https://lore.kernel.org/linux-trace-kernel/175366879192.487099.5714468217360139639.stgit@mhiramat.tok.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google)

tracing: fprobe-event: Allocate string buffers from heap

2025-07-23T15:21:37+00:00

Allocate temporary string buffers for fprobe-event from heap
instead of stack. This fixes the stack frame exceed limit error.

Link: https://lore.kernel.org/all/175323426643.57270.6657152008331160704.stgit@devnote2/

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202506240416.nZIhDXoO-lkp@intel.com/
Signed-off-by: Masami Hiramatsu (Google) 
Reviewed-by: Steven Rostedt (Google)

tracing: probe: Allocate traceprobe_parse_context from heap

2025-07-23T15:21:30+00:00

Instead of allocating traceprobe_parse_context on stack, allocate it
dynamically from heap (slab).

This change is likely intended to prevent potential stack overflow
issues, which can be a concern in the kernel environment where stack
space is limited.

Link: https://lore.kernel.org/all/175323425650.57270.280750740753792504.stgit@devnote2/

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202506240416.nZIhDXoO-lkp@intel.com/
Signed-off-by: Masami Hiramatsu (Google) 
Reviewed-by: Steven Rostedt (Google)

tracing: probes: Sort #include alphabetically

2025-07-23T15:21:22+00:00

Sort the #include directives in trace_probe* files alphabetically for
easier maintenance and avoid double includes.
This also groups headers as linux-generic, asm-generic, and local
headers.

Link: https://lore.kernel.org/all/175323424678.57270.11975372127870059007.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google)

tracing: tprobe-events: Register tracepoint when enable tprobe event

2025-07-02T00:45:35+00:00

As same as fprobe, register tracepoint stub function only when enabling
tprobe events. The major changes are introducing a list of
tracepoint_user and its lock, and tprobe_event_module_nb, which is
another module notifier for module loading/unloading.  By spliting the
lock from event_mutex and a module notifier for trace_fprobe, it
solved AB-BA lock dependency issue between event_mutex and
tracepoint_module_list_mutex.

Link: https://lore.kernel.org/all/174343538901.843280.423773753642677941.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google)

tracing: fprobe-events: Register fprobe-events only when it is enabled

2025-07-02T00:45:09+00:00

Currently fprobe events are registered when it is defined. Thus it will
give some overhead even if it is disabled. This changes it to register the
fprobe only when it is enabled.

Link: https://lore.kernel.org/all/174343537128.843280.16131300052837035043.stgit@devnote2/

Suggested-by: Steven Rostedt 
Signed-off-by: Masami Hiramatsu (Google)

tracing: tprobe-events: Support multiple tprobes on the same tracepoint

2025-07-02T00:44:55+00:00

Allow user to set multiple tracepoint-probe events on the same
tracepoint. After the last tprobe-event is removed, the tracepoint
callback is unregistered.

Link: https://lore.kernel.org/all/174343536245.843280.6548776576601537671.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google)