linux-stable.git/kernel/trace/trace_uprobe.c, branch v5.15.209

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

2025-10-19T14:21:51+00:00

[ Upstream commit 9cf9aa7b0acfde7545c1a1d912576e9bab28dc6f ]

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) 
[ Drop fprobe changes + context ]
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

tracing: probes: Fix a possible race in trace_probe_log APIs

2025-05-22T12:08:21+00:00

[ Upstream commit fd837de3c9cb1a162c69bc1fb1f438467fe7f2f5 ]

Since the shared trace_probe_log variable can be accessed and
modified via probe event create operation of kprobe_events,
uprobe_events, and dynamic_events, it should be protected.
In the dynamic_events, all operations are serialized by
`dyn_event_ops_mutex`. But kprobe_events and uprobe_events
interfaces are not serialized.

To solve this issue, introduces dyn_event_create(), which runs
create() operation under the mutex, for kprobe_events and
uprobe_events. This also uses lockdep to check the mutex is
held when using trace_probe_log* APIs.

Link: https://lore.kernel.org/all/174684868120.551552.3068655787654268804.stgit@devnote2/

Reported-by: Paul Cacheux 
Closes: https://lore.kernel.org/all/20250510074456.805a16872b591e2971a4d221@kernel.org/
Fixes: ab105a4fb894 ("tracing: Use tracing error_log with probe events")
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin

bpf: Clear the probe_addr for uprobe

2023-09-19T10:22:32+00:00

[ Upstream commit 5125e757e62f6c1d5478db4c2b61a744060ddf3f ]

To avoid returning uninitialized or random values when querying the file
descriptor (fd) and accessing probe_addr, it is necessary to clear the
variable prior to its use.

Fixes: 41bdc4b40ed6 ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
Signed-off-by: Yafang Shao 
Acked-by: Yonghong Song 
Acked-by: Jiri Olsa 
Link: https://lore.kernel.org/r/20230709025630.3735-6-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Sasha Levin

tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails

2023-08-03T08:22:31+00:00

[ Upstream commit 797311bce5c2ac90b8d65e357603cfd410d36ebb ]

Fix to record 0-length data to data_loc in fetch_store_string*() if it fails
to get the string data.
Currently those expect that the data_loc is updated by store_trace_args() if
it returns the error code. However, that does not work correctly if the
argument is an array of strings. In that case, store_trace_args() only clears
the first entry of the array (which may have no error) and leaves other
entries. So it should be cleared by fetch_store_string*() itself.
Also, 'dyndata' and 'maxlen' in store_trace_args() should be updated
only if it is used (ret > 0 and argument is a dynamic data.)

Link: https://lore.kernel.org/all/168908496683.123124.4761206188794205601.stgit@devnote2/

Fixes: 40b53b771806 ("tracing: probeevent: Add array type support")
Cc: stable@vger.kernel.org
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin

tracing/uprobes: Check the return value of kstrdup() for tu->filename

2022-03-08T18:12:38+00:00

[ Upstream commit 8c7224245557707c613f130431cafbaaa4889615 ]

kstrdup() returns NULL when some internal memory errors happen, it is
better to check the return value of it so to catch the memory error in
time.

Link: https://lkml.kernel.org/r/tencent_3C2E330722056D7891D2C83F29C802734B06@qq.com

Acked-by: Masami Hiramatsu 
Fixes: 33ea4b24277b ("perf/core: Implement the 'perf_uprobe' PMU")
Signed-off-by: Xiaoke Wang 
Signed-off-by: Steven Rostedt 
Signed-off-by: Sasha Levin

tracing/uprobe: Fix uprobe_perf_open probes iteration

2021-12-01T08:04:43+00:00

commit 1880ed71ce863318c1ce93bf324876fb5f92854f upstream.

Add missing 'tu' variable initialization in the probes loop,
otherwise the head 'tu' is used instead of added probes.

Link: https://lkml.kernel.org/r/20211123142801.182530-1-jolsa@kernel.org

Cc: stable@vger.kernel.org
Fixes: 99c9a923e97a ("tracing/uprobe: Fix double perf_event linking on multiprobe uprobe")
Acked-by: Masami Hiramatsu 
Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Greg Kroah-Hartman

tracing: Disable "other" permission bits in the tracefs files

2021-11-18T18:16:15+00:00

[ Upstream commit 21ccc9cd72116289469e5519b6159c675a2fa58f ]

When building the files in the tracefs file system, do not by default set
any permissions for OTH (other). This will make it easier for admins who
want to define a group for accessing tracefs and not having to first
disable all the permission bits for "other" in the file system.

As tracing can leak sensitive information, it should never by default
allowing all users access. An admin can still set the permission bits for
others to have access, which may be useful for creating a honeypot and
seeing who takes advantage of it and roots the machine.

Link: https://lkml.kernel.org/r/20210818153038.864149276@goodmis.org

Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Sasha Levin

tracing/probes: Reject events which have the same name of existing one

2021-08-19T13:15:19+00:00

Since kprobe_events and uprobe_events only check whether the
other same-type probe event has the same name or not, if the
user gives the same name of the existing tracepoint event (or
the other type of probe events), it silently fails to create
the tracefs entry (but registered.) as below.

/sys/kernel/tracing # ls events/task/task_rename
enable   filter   format   hist     id       trigger
/sys/kernel/tracing # echo p:task/task_rename vfs_read >> kprobe_events
[  113.048508] Could not create tracefs 'task_rename' directory
/sys/kernel/tracing # cat kprobe_events
p:task/task_rename vfs_read

To fix this issue, check whether the existing events have the
same name or not in trace_probe_register_event_call(). If exists,
it rejects to register the new event.

Link: https://lkml.kernel.org/r/162936876189.187130.17558311387542061930.stgit@devnote2

Signed-off-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (VMware)

tracing/probes: Have process_fetch_insn() take a void * instead of pt_regs

2021-08-19T13:09:03+00:00

In preparation to allow event probes to use the process_fetch_insn()
callback in trace_probe_tmpl.h, change the data passed to it from a
pointer to pt_regs, as the event probe will not be using regs, and make it
a void pointer instead.

Update the process_fetch_insn() callers for kprobe and uprobe events to
have the regs defined in the function and just typecast the void pointer
parameter.

Link: https://lkml.kernel.org/r/20210819041842.291622924@goodmis.org

Acked-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (VMware)

tracing/probe: Change traceprobe_set_print_fmt() to take a type

2021-08-19T13:08:29+00:00

Instead of a boolean "is_return" have traceprobe_set_print_fmt() take a
type (currently just PROBE_PRINT_NORMAL and PROBE_PRINT_RETURN). This will
simplify adding different types. For example, the development of the
event_probe, will need its own type as it prints an event, and not an IP.

Link: https://lkml.kernel.org/r/20210819041842.104626301@goodmis.org

Acked-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt (VMware)