linux.git/kernel/kprobes.c, branch v6.1.168

kprobes: Remove unneeded warnings from __arm_kprobe_ftrace()

2026-03-25T10:03:16+00:00

[ Upstream commit 5ef268cb7a0aac55521fd9881f1939fa94a8988e ]

Remove unneeded warnings for handled errors from __arm_kprobe_ftrace()
because all caller handled the error correctly.

Link: https://lore.kernel.org/all/177261531182.1312989.8737778408503961141.stgit@mhiramat.tok.corp.google.com/

Reported-by: Zw Tang 
Closes: https://lore.kernel.org/all/CAPHJ_V+J6YDb_wX2nhXU6kh466Dt_nyDSas-1i_Y8s7tqY-Mzw@mail.gmail.com/
Fixes: 9c89bb8e3272 ("kprobes: treewide: Cleanup the error messages for kprobes")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

kprobes: Remove unneeded goto

2026-03-25T10:03:16+00:00

[ Upstream commit 5e5b8b49335971b68b54afeb0e7ded004945af07 ]

Remove unneeded gotos. Since the labels referred by these gotos have
only one reference for each, we can replace those gotos with the
referred code.

Link: https://lore.kernel.org/all/173371211203.480397.13988907319659165160.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) 
Stable-dep-of: 5ef268cb7a0a ("kprobes: Remove unneeded warnings from __arm_kprobe_ftrace()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

kprobes: Fix to check symbol prefixes correctly

2024-08-14T11:52:54+00:00

[ Upstream commit 8c8acb8f26cbde665b233dd1b9bbcbb9b86822dc ]

Since str_has_prefix() takes the prefix as the 2nd argument and the string
as the first, is_cfi_preamble_symbol() always fails to check the prefix.
Fix the function parameter order so that it correctly check the prefix.

Link: https://lore.kernel.org/all/172260679559.362040.7360872132937227206.stgit@devnote2/

Fixes: de02f2ac5d8c ("kprobes: Prohibit probing on CFI preamble symbol")
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin

kprobes: Fix possible use-after-free issue on kprobe registration

2024-04-17T09:18:27+00:00

commit 325f3fb551f8cd672dbbfc4cf58b14f9ee3fc9e8 upstream.

When unloading a module, its state is changing MODULE_STATE_LIVE ->
 MODULE_STATE_GOING -> MODULE_STATE_UNFORMED. Each change will take
a time. `is_module_text_address()` and `__module_text_address()`
works with MODULE_STATE_LIVE and MODULE_STATE_GOING.
If we use `is_module_text_address()` and `__module_text_address()`
separately, there is a chance that the first one is succeeded but the
next one is failed because module->state becomes MODULE_STATE_UNFORMED
between those operations.

In `check_kprobe_address_safe()`, if the second `__module_text_address()`
is failed, that is ignored because it expected a kernel_text address.
But it may have failed simply because module->state has been changed
to MODULE_STATE_UNFORMED. In this case, arm_kprobe() will try to modify
non-exist module text address (use-after-free).

To fix this problem, we should not use separated `is_module_text_address()`
and `__module_text_address()`, but use only `__module_text_address()`
once and do `try_module_get(module)` which is only available with
MODULE_STATE_LIVE.

Link: https://lore.kernel.org/all/20240410015802.265220-1-zhengyejian1@huawei.com/

Fixes: 28f6c37a2910 ("kprobes: Forbid probing on trampoline and BPF code areas")
Cc: stable@vger.kernel.org
Signed-off-by: Zheng Yejian 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

kprobes: consistent rcu api usage for kretprobe holder

2023-12-13T17:39:17+00:00

commit d839a656d0f3caca9f96e9bf912fd394ac6a11bc upstream.

It seems that the pointer-to-kretprobe "rp" within the kretprobe_holder is
RCU-managed, based on the (non-rethook) implementation of get_kretprobe().
The thought behind this patch is to make use of the RCU API where possible
when accessing this pointer so that the needed barriers are always in place
and to self-document the code.

The __rcu annotation to "rp" allows for sparse RCU checking. Plain writes
done to the "rp" pointer are changed to make use of the RCU macro for
assignment. For the single read, the implementation of get_kretprobe()
is simplified by making use of an RCU macro which accomplishes the same,
but note that the log warning text will be more generic.

I did find that there is a difference in assembly generated between the
usage of the RCU macros vs without. For example, on arm64, when using
rcu_assign_pointer(), the corresponding store instruction is a
store-release (STLR) which has an implicit barrier. When normal assignment
is done, a regular store (STR) is found. In the macro case, this seems to
be a result of rcu_assign_pointer() using smp_store_release() when the
value to write is not NULL.

Link: https://lore.kernel.org/all/20231122132058.3359-1-inwardvessel@gmail.com/

Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash")
Cc: stable@vger.kernel.org
Signed-off-by: JP Kobryn 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

kprobes: Prohibit probing on CFI preamble symbol

2023-09-13T07:42:23+00:00

[ Upstream commit de02f2ac5d8cfb311f44f2bf144cc20002f1fbbd ]

Do not allow to probe on "__cfi_" or "__pfx_" started symbol, because those
are used for CFI and not executed. Probing it will break the CFI.

Link: https://lore.kernel.org/all/168904024679.116016.18089228029322008512.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) 
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Sasha Levin

kprobes: Fix to handle forcibly unoptimized kprobes on freeing_list

2023-03-10T08:34:27+00:00

commit 4fbd2f83fda0ca44a2ec6421ca3508b355b31858 upstream.

Since forcibly unoptimized kprobes will be put on the freeing_list directly
in the unoptimize_kprobe(), do_unoptimize_kprobes() must continue to check
the freeing_list even if unoptimizing_list is empty.

This bug can happen if a kprobe is put in an instruction which is in the
middle of the jump-replaced instruction sequence of an optprobe, *and* the
optprobe is recently unregistered and queued on unoptimizing_list.
In this case, the optprobe will be unoptimized forcibly (means immediately)
and put it into the freeing_list, expecting the optprobe will be handled in
do_unoptimize_kprobe().
But if there is no other optprobes on the unoptimizing_list, current code
returns from the do_unoptimize_kprobe() soon and does not handle the
optprobe which is on the freeing_list. Then the optprobe will hit the
WARN_ON_ONCE() in the do_free_cleaned_kprobes(), because it is not handled
in the latter loop of the do_unoptimize_kprobe().

To solve this issue, do not return from do_unoptimize_kprobes() immediately
even if unoptimizing_list is empty.

Moreover, this change affects another case. kill_optimized_kprobes() expects
kprobe_optimizer() will just free the optprobe on freeing_list.
So I changed it to just do list_move() to freeing_list if optprobes are on
unoptimizing list. And the do_unoptimize_kprobe() will skip
arch_disarm_kprobe() if the probe on freeing_list has gone flag.

Link: https://lore.kernel.org/all/Y8URdIfVr3pq2X8w@xpf.sh.intel.com/
Link: https://lore.kernel.org/all/167448024501.3253718.13037333683110512967.stgit@devnote3/

Fixes: e4add247789e ("kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic")
Reported-by: Pengfei Xu 
Signed-off-by: Masami Hiramatsu (Google) 
Cc: stable@vger.kernel.org
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

x86/kprobes: Fix arch_check_optimized_kprobe check within optimized_kprobe range

2023-03-10T08:34:13+00:00

commit f1c97a1b4ef709e3f066f82e3ba3108c3b133ae6 upstream.

When arch_prepare_optimized_kprobe calculating jump destination address,
it copies original instructions from jmp-optimized kprobe (see
__recover_optprobed_insn), and calculated based on length of original
instruction.

arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when
checking whether jmp-optimized kprobe exists.
As a result, setup_detour_execution may jump to a range that has been
overwritten by jump destination address, resulting in an inval opcode error.

For example, assume that register two kprobes whose addresses are
 and  in "func" function.
The original code of "func" function is as follows:

   0xffffffff816cb5e9 <+9>:     push   %r12
   0xffffffff816cb5eb <+11>:    xor    %r12d,%r12d
   0xffffffff816cb5ee <+14>:    test   %rdi,%rdi
   0xffffffff816cb5f1 <+17>:    setne  %r12b
   0xffffffff816cb5f5 <+21>:    push   %rbp

1.Register the kprobe for , assume that is kp1, corresponding optimized_kprobe is op1.
  After the optimization, "func" code changes to:

   0xffffffff816cc079 <+9>:     push   %r12
   0xffffffff816cc07b <+11>:    jmp    0xffffffffa0210000
   0xffffffff816cc080 <+16>:    incl   0xf(%rcx)
   0xffffffff816cc083 <+19>:    xchg   %eax,%ebp
   0xffffffff816cc084 <+20>:    (bad)
   0xffffffff816cc085 <+21>:    push   %rbp

Now op1->flags == KPROBE_FLAG_OPTIMATED;

2. Register the kprobe for , assume that is kp2, corresponding optimized_kprobe is op2.

register_kprobe(kp2)
  register_aggr_kprobe
    alloc_aggr_kprobe
      __prepare_optimized_kprobe
        arch_prepare_optimized_kprobe
          __recover_optprobed_insn    // copy original bytes from kp1->optinsn.copied_insn,
                                      // jump address = 

3. disable kp1:

disable_kprobe(kp1)
  __disable_kprobe
    ...
    if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
      ret = disarm_kprobe(orig_p, true)       // add op1 in unoptimizing_list, not unoptimized
      orig_p->flags |= KPROBE_FLAG_DISABLED;  // op1->flags ==  KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED
    ...

4. unregister kp2
__unregister_kprobe_top
  ...
  if (!kprobe_disabled(ap) && !kprobes_all_disarmed) {
    optimize_kprobe(op)
      ...
      if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return
        return;
      p->kp.flags |= KPROBE_FLAG_OPTIMIZED;   //  now op2 has KPROBE_FLAG_OPTIMIZED
  }

"func" code now is:

   0xffffffff816cc079 <+9>:     int3
   0xffffffff816cc07a <+10>:    push   %rsp
   0xffffffff816cc07b <+11>:    jmp    0xffffffffa0210000
   0xffffffff816cc080 <+16>:    incl   0xf(%rcx)
   0xffffffff816cc083 <+19>:    xchg   %eax,%ebp
   0xffffffff816cc084 <+20>:    (bad)
   0xffffffff816cc085 <+21>:    push   %rbp

5. if call "func", int3 handler call setup_detour_execution:

  if (p->flags & KPROBE_FLAG_OPTIMIZED) {
    ...
    regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
    ...
  }

The code for the destination address is

   0xffffffffa021072c:  push   %r12
   0xffffffffa021072e:  xor    %r12d,%r12d
   0xffffffffa0210731:  jmp    0xffffffff816cb5ee 

However,  is not a valid start instruction address. As a result, an error occurs.

Link: https://lore.kernel.org/all/20230216034247.32348-3-yangjihong1@huawei.com/

Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
Signed-off-by: Yang Jihong 
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

x86/kprobes: Fix __recover_optprobed_insn check optimizing logic

2023-03-10T08:34:13+00:00

commit 868a6fc0ca2407622d2833adefe1c4d284766c4c upstream.

Since the following commit:

  commit f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")

modified the update timing of the KPROBE_FLAG_OPTIMIZED, a optimized_kprobe
may be in the optimizing or unoptimizing state when op.kp->flags
has KPROBE_FLAG_OPTIMIZED and op->list is not empty.

The __recover_optprobed_insn check logic is incorrect, a kprobe in the
unoptimizing state may be incorrectly determined as unoptimizing.
As a result, incorrect instructions are copied.

The optprobe_queued_unopt function needs to be exported for invoking in
arch directory.

Link: https://lore.kernel.org/all/20230216034247.32348-2-yangjihong1@huawei.com/

Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")
Cc: stable@vger.kernel.org
Signed-off-by: Yang Jihong 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

kprobes: kretprobe events missing on 2-core KVM guest

2023-01-04T10:28:58+00:00

[ Upstream commit 3b7ddab8a19aefc768f345fd3782af35b4a68d9b ]

Default value of maxactive is set as num_possible_cpus() for nonpreemptable
systems. For a 2-core system, only 2 kretprobe instances would be allocated
in default, then these 2 instances for execve kretprobe are very likely to
be used up with a pipelined command.

Here's the testcase: a shell script was added to crontab, and the content
of the script is:

  #!/bin/sh
  do_something_magic `tr -dc a-z < /dev/urandom | head -c 10`

cron will trigger a series of program executions (4 times every hour). Then
events loss would be noticed normally after 3-4 hours of testings.

The issue is caused by a burst of series of execve requests. The best number
of kretprobe instances could be different case by case, and should be user's
duty to determine, but num_possible_cpus() as the default value is inadequate
especially for systems with small number of cpus.

This patch enables the logic for preemption as default, thus increases the
minimum of maxactive to 10 for nonpreemptable systems.

Link: https://lore.kernel.org/all/20221110081502.492289-1-wuqiang.matt@bytedance.com/

Signed-off-by: wuqiang 
Reviewed-by: Solar Designer 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin