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Yuan Chen 5ebea65616 tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 
commit 9cf9aa7b0a upstream.

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 <kprobe_perf_func+0x2c>:     ldr     x21, [x24,#120]
include/linux/compiler.h: 294
0xffff3df8995039f0 <kprobe_perf_func+0x30>:     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: 50d7805607 ("tracing/kprobes: Add probe handler dispatcher to support perf and ftrace concurrent use")
Cc: stable@vger.kernel.org
Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-15 12:04:17 +02:00
arch sparc: fix accurate exception reporting in copy_{from,to}_user for M7 2025-10-15 12:04:03 +02:00
block blk-throttle: fix throtl_data leak during disk release 2025-10-15 12:03:34 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto KEYS: X.509: Fix Basic Constraints CA flag parsing 2025-10-15 12:04:11 +02:00
Documentation Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram 2025-10-15 12:04:01 +02:00
drivers mfd: vexpress-sysreg: Check the return value of devm_gpiochip_add_data() 2025-10-15 12:04:17 +02:00
fs fs: udf: fix OOB read in lengthAllocDescs handling 2025-10-15 12:04:16 +02:00
include nfs/localio: avoid issuing misaligned IO using O_DIRECT 2025-10-15 12:04:13 +02:00
init Fix CC_HAS_ASM_GOTO_OUTPUT on non-x86 architectures 2025-10-15 12:03:13 +02:00
io_uring io_uring/zcrx: fix overshooting recv limit 2025-10-15 12:04:15 +02:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel tracing: Fix race condition in kprobe initialization causing NULL pointer dereference 2025-10-15 12:04:17 +02:00
lib vdso/datastore: Gate time data behind CONFIG_GENERIC_GETTIMEOFDAY 2025-10-15 12:03:24 +02:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slub: Fix cmp_loc_by_count() to return 0 when counts are equal 2025-10-15 12:03:56 +02:00
net net: nfc: nci: Add parameter validation for packet data 2025-10-15 12:04:16 +02:00
rust rust: cpumask: Mark CpumaskVar as transparent 2025-10-15 12:03:19 +02:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts scripts/misc-check: update export checks for EXPORT_SYMBOL_FOR_MODULES() 2025-10-15 12:03:22 +02:00
security lsm: CONFIG_LSM can depend on CONFIG_SECURITY 2025-10-15 12:03:17 +02:00
sound ASoC: SOF: ipc4-pcm: fix start offset calculation for chain DMA 2025-10-15 12:04:16 +02:00
tools selftests/bpf: Fix realloc size in bpf_get_addrs 2025-10-15 12:04:14 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap 7 hotfixes. 4 are cc:stable and the remainder address post-6.16 issues or 2025-09-28 09:32:00 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc8 2025-09-28 13:19:23 -07:00
Makefile Linux 6.17.2 2025-10-12 13:01:58 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.