The second argument of bpf_sysctl_get_name() helper is a pointer to a
buffer that is being written to. However that isn't specify in the
prototype.

Until commit 37cce22dbd51a ("bpf: verifier: Refactor helper access
type tracking"), all helper accesses were considered as a possible
write access by the verifier, so no big harm was done. However, since
then, the verifier might make wrong asssumption about the content of
that address which might lead it to make faulty optimizations (such as
removing code that was wrongly labeled dead). This is what happens in
test_sysctl selftest to the tests related to sysctl_get_name.

Add MEM_WRITE flag the second argument of bpf_sysctl_get_name().

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250619140603.148942-2-jmarchan@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Pull bpf updates from Alexei Starovoitov:

 - Fix and improve BTF deduplication of identical BTF types (Alan
   Maguire and Andrii Nakryiko)

 - Support up to 12 arguments in BPF trampoline on arm64 (Xu Kuohai and
   Alexis Lothoré)

 - Support load-acquire and store-release instructions in BPF JIT on
   riscv64 (Andrea Parri)

 - Fix uninitialized values in BPF_{CORE,PROBE}_READ macros (Anton
   Protopopov)

 - Streamline allowed helpers across program types (Feng Yang)

 - Support atomic update for hashtab of BPF maps (Hou Tao)

 - Implement json output for BPF helpers (Ihor Solodrai)

 - Several s390 JIT fixes (Ilya Leoshkevich)

 - Various sockmap fixes (Jiayuan Chen)

 - Support mmap of vmlinux BTF data (Lorenz Bauer)

 - Support BPF rbtree traversal and list peeking (Martin KaFai Lau)

 - Tests for sockmap/sockhash redirection (Michal Luczaj)

 - Introduce kfuncs for memory reads into dynptrs (Mykyta Yatsenko)

 - Add support for dma-buf iterators in BPF (T.J. Mercier)

 - The verifier support for __bpf_trap() (Yonghong Song)

* tag 'bpf-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (135 commits)
  bpf, arm64: Remove unused-but-set function and variable.
  selftests/bpf: Add tests with stack ptr register in conditional jmp
  bpf: Do not include stack ptr register in precision backtracking bookkeeping
  selftests/bpf: enable many-args tests for arm64
  bpf, arm64: Support up to 12 function arguments
  bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem()
  bpf: Avoid __bpf_prog_ret0_warn when jit fails
  bpftool: Add support for custom BTF path in prog load/loadall
  selftests/bpf: Add unit tests with __bpf_trap() kfunc
  bpf: Warn with __bpf_trap() kfunc maybe due to uninitialized variable
  bpf: Remove special_kfunc_set from verifier
  selftests/bpf: Add test for open coded dmabuf_iter
  selftests/bpf: Add test for dmabuf_iter
  bpf: Add open coded dmabuf iterator
  bpf: Add dmabuf iterator
  dma-buf: Rename debugfs symbols
  bpf: Fix error return value in bpf_copy_from_user_dynptr
  libbpf: Use mmap to parse vmlinux BTF from sysfs
  selftests: bpf: Add a test for mmapable vmlinux BTF
  btf: Allow mmap of vmlinux btf
  ...

Replace explicit cgroup_bpf_inherit/offline() calls from cgroup
creation/destruction paths with notification callback registered on
cgroup_lifetime_notifier.

Signed-off-by: Tejun Heo <tj@kernel.org>

if it works under NMI and doesn't use any context-dependent things,
should be fine for any program type. The detailed discussion is in [1].

[1] https://lore.kernel.org/all/CAEf4Bza6gK3dsrTosk6k3oZgtHesNDSrDd8sdeQ-GiS6oJixQg@mail.gmail.com/

Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/bpf/20250506061434.94277-2-yangfeng59949@163.com

Currently for bpf progs in a cgroup hierarchy, the effective prog array
is computed from bottom cgroup to upper cgroups (post-ordering). For
example, the following cgroup hierarchy
    root cgroup: p1, p2
        subcgroup: p3, p4
have BPF_F_ALLOW_MULTI for both cgroup levels.
The effective cgroup array ordering looks like
    p3 p4 p1 p2
and at run time, progs will execute based on that order.

But in some cases, it is desirable to have root prog executes earlier than
children progs (pre-ordering). For example,
  - prog p1 intends to collect original pkt dest addresses.
  - prog p3 will modify original pkt dest addresses to a proxy address for
    security reason.
The end result is that prog p1 gets proxy address which is not what it
wants. Putting p1 to every child cgroup is not desirable either as it
will duplicate itself in many child cgroups. And this is exactly a use case
we are encountering in Meta.

To fix this issue, let us introduce a flag BPF_F_PREORDER. If the flag
is specified at attachment time, the prog has higher priority and the
ordering with that flag will be from top to bottom (pre-ordering).
For example, in the above example,
    root cgroup: p1, p2
        subcgroup: p3, p4
Let us say p2 and p4 are marked with BPF_F_PREORDER. The final
effective array ordering will be
    p2 p4 p3 p1

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250224230116.283071-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Pull sysctl updates from Joel Granados:
 "sysctl ctl_table constification:

   - Constifying ctl_table structs prevents the modification of
     proc_handler function pointers. All ctl_table struct arguments are
     const qualified in the sysctl API in such a way that the ctl_table
     arrays being defined elsewhere and passed through sysctl can be
     constified one-by-one.

     We kick the constification off by qualifying user_table in
     kernel/ucount.c and expect all the ctl_tables to be constified in
     the coming releases.

  Misc fixes:

   - Adjust comments in two places to better reflect the code

   - Remove superfluous dput calls

   - Remove Luis from sysctl maintainership

   - Replace comments about holding a lock with calls to
     lockdep_assert_held"

* tag 'sysctl-6.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
  sysctl: Reduce dput(child) calls in proc_sys_fill_cache()
  sysctl: Reorganize kerneldoc parameter names
  ucounts: constify sysctl table user_table
  sysctl: update comments to new registration APIs
  MAINTAINERS: remove me from sysctl
  sysctl: Convert locking comments to lockdep assertions
  const_structs.checkpatch: add ctl_table
  sysctl: make internal ctl_tables const
  sysctl: allow registration of const struct ctl_table
  sysctl: move internal interfaces to const struct ctl_table
  bpf: Constify ctl_table argument of filter function

The sysctl core is moving to allow "struct ctl_table" in read-only memory.
As a preparation for that all functions handling "struct ctl_table" need
to be able to work with "const struct ctl_table".
As __cgroup_bpf_run_filter_sysctl() does not modify its table, it can be
adapted trivially.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Joel Granados <joel.granados@kernel.org>

A hung_task problem shown below was found:

INFO: task kworker/0:0:8 blocked for more than 327 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Workqueue: events cgroup_bpf_release
Call Trace:
 <TASK>
 __schedule+0x5a2/0x2050
 ? find_held_lock+0x33/0x100
 ? wq_worker_sleeping+0x9e/0xe0
 schedule+0x9f/0x180
 schedule_preempt_disabled+0x25/0x50
 __mutex_lock+0x512/0x740
 ? cgroup_bpf_release+0x1e/0x4d0
 ? cgroup_bpf_release+0xcf/0x4d0
 ? process_scheduled_works+0x161/0x8a0
 ? cgroup_bpf_release+0x1e/0x4d0
 ? mutex_lock_nested+0x2b/0x40
 ? __pfx_delay_tsc+0x10/0x10
 mutex_lock_nested+0x2b/0x40
 cgroup_bpf_release+0xcf/0x4d0
 ? process_scheduled_works+0x161/0x8a0
 ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
 ? process_scheduled_works+0x161/0x8a0
 process_scheduled_works+0x23a/0x8a0
 worker_thread+0x231/0x5b0
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x14d/0x1c0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x59/0x70
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1b/0x30
 </TASK>

This issue can be reproduced by the following pressuse test:
1. A large number of cpuset cgroups are deleted.
2. Set cpu on and off repeatly.
3. Set watchdog_thresh repeatly.
The scripts can be obtained at LINK mentioned above the signature.

The reason for this issue is cgroup_mutex and cpu_hotplug_lock are
acquired in different tasks, which may lead to deadlock.
It can lead to a deadlock through the following steps:
1. A large number of cpusets are deleted asynchronously, which puts a
   large number of cgroup_bpf_release works into system_wq. The max_active
   of system_wq is WQ_DFL_ACTIVE(256). Consequently, all active works are
   cgroup_bpf_release works, and many cgroup_bpf_release works will be put
   into inactive queue. As illustrated in the diagram, there are 256 (in
   the acvtive queue) + n (in the inactive queue) works.
2. Setting watchdog_thresh will hold cpu_hotplug_lock.read and put
   smp_call_on_cpu work into system_wq. However step 1 has already filled
   system_wq, 'sscs.work' is put into inactive queue. 'sscs.work' has
   to wait until the works that were put into the inacvtive queue earlier
   have executed (n cgroup_bpf_release), so it will be blocked for a while.
3. Cpu offline requires cpu_hotplug_lock.write, which is blocked by step 2.
4. Cpusets that were deleted at step 1 put cgroup_release works into
   cgroup_destroy_wq. They are competing to get cgroup_mutex all the time.
   When cgroup_metux is acqured by work at css_killed_work_fn, it will
   call cpuset_css_offline, which needs to acqure cpu_hotplug_lock.read.
   However, cpuset_css_offline will be blocked for step 3.
5. At this moment, there are 256 works in active queue that are
   cgroup_bpf_release, they are attempting to acquire cgroup_mutex, and as
   a result, all of them are blocked. Consequently, sscs.work can not be
   executed. Ultimately, this situation leads to four processes being
   blocked, forming a deadlock.

system_wq(step1)		WatchDog(step2)			cpu offline(step3)	cgroup_destroy_wq(step4)
...
2000+ cgroups deleted asyn
256 actives + n inactives
				__lockup_detector_reconfigure
				P(cpu_hotplug_lock.read)
				put sscs.work into system_wq
256 + n + 1(sscs.work)
sscs.work wait to be executed
				warting sscs.work finish
								percpu_down_write
								P(cpu_hotplug_lock.write)
								...blocking...
											css_killed_work_fn
											P(cgroup_mutex)
											cpuset_css_offline
											P(cpu_hotplug_lock.read)
											...blocking...
256 cgroup_bpf_release
mutex_lock(&cgroup_mutex);
..blocking...

To fix the problem, place cgroup_bpf_release works on a dedicated
workqueue which can break the loop and solve the problem. System wqs are
for misc things which shouldn't create a large number of concurrent work
items. If something is going to generate >WQ_DFL_ACTIVE(256) concurrent
work items, it should use its own dedicated workqueue.

Fixes: 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself")
Cc: stable@vger.kernel.org # v5.3+
Link: https://lore.kernel.org/cgroups/e90c32d2-2a85-4f28-9154-09c7d320cb60@huawei.com/T/#t
Tested-by: Vishal Chourasia <vishalc@linux.ibm.com>
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

The helper bpf_current_task_under_cgroup() currently is only allowed for
tracing programs, allow its usage also in the BPF_CGROUP_* program types.

Move the code from kernel/trace/bpf_trace.c to kernel/bpf/helpers.c,
so it compiles also without CONFIG_BPF_EVENTS.

This will be used in systemd-networkd to monitor the sysctl writes,
and filter it's own writes from others:
https://github.com/systemd/systemd/pull/32212

Signed-off-by: Matteo Croce <teknoraver@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240819162805.78235-3-technoboy85@gmail.com

Currently bpf_get_current_pid_tgid() is allowed in tracing, cgroup
and sk_msg progs while bpf_get_ns_current_pid_tgid() is only allowed
in tracing progs.

We have an internal use case where for an application running
in a container (with pid namespace), user wants to get
the pid associated with the pid namespace in a cgroup bpf
program. Currently, cgroup bpf progs already allow
bpf_get_current_pid_tgid(). Let us allow bpf_get_ns_current_pid_tgid()
as well.

With auditing the code, bpf_get_current_pid_tgid() is also used
by sk_msg prog. But there are no side effect to expose these two
helpers to all prog types since they do not reveal any kernel specific
data. The detailed discussion is in [1].

So with this patch, both bpf_get_current_pid_tgid() and bpf_get_ns_current_pid_tgid()
are put in bpf_base_func_proto(), making them available to all
program types.

  [1] https://lore.kernel.org/bpf/20240307232659.1115872-1-yonghong.song@linux.dev/

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240315184854.2975190-1-yonghong.song@linux.dev