linux.git/kernel/bpf/cgroup.c, branch v6.1.168

bpf: Reject narrower access to pointer ctx fields

2026-02-06T15:44:14+00:00

commit e09299225d5ba3916c91ef70565f7d2187e4cca0 upstream.

The following BPF program, simplified from a syzkaller repro, causes a
kernel warning:

    r0 = *(u8 *)(r1 + 169);
    exit;

With pointer field sk being at offset 168 in __sk_buff. This access is
detected as a narrower read in bpf_skb_is_valid_access because it
doesn't match offsetof(struct __sk_buff, sk). It is therefore allowed
and later proceeds to bpf_convert_ctx_access. Note that for the
"is_narrower_load" case in the convert_ctx_accesses(), the insn->off
is aligned, so the cnt may not be 0 because it matches the
offsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. However,
the target_size stays 0 and the verifier errors with a kernel warning:

    verifier bug: error during ctx access conversion(1)

This patch fixes that to return a proper "invalid bpf_context access
off=X size=Y" error on the load instruction.

The same issue affects multiple other fields in context structures that
allow narrow access. Some other non-affected fields (for sk_msg,
sk_lookup, and sockopt) were also changed to use bpf_ctx_range_ptr for
consistency.

Note this syzkaller crash was reported in the "Closes" link below, which
used to be about a different bug, fixed in
commit fce7bd8e385a ("bpf/verifier: Handle BPF_LOAD_ACQ instructions
in insn_def_regno()"). Because syzbot somehow confused the two bugs,
the new crash and repro didn't get reported to the mailing list.

Fixes: f96da09473b52 ("bpf: simplify narrower ctx access")
Fixes: 0df1a55afa832 ("bpf: Warn on internal verifier errors")
Reported-by: syzbot+0ef84a7bdf5301d4cbec@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0ef84a7bdf5301d4cbec
Signed-off-by: Paul Chaignon 
Signed-off-by: Martin KaFai Lau 
Acked-by: Eduard Zingerman 
Link: https://patch.msgid.link/3b8dcee67ff4296903351a974ddd9c4dca768b64.1753194596.git.paul.chaignon@gmail.com
[shung-hsi.yu: offset(struct bpf_sock_ops, skb_hwtstamp) case was
dropped becasuse it was only added in v6.2 with commit 9bb053490f1a
("bpf: Add hwtstamp field for the sockops prog")]
Signed-off-by: Shung-Hsi Yu 
Signed-off-by: Greg Kroah-Hartman

cgroup/bpf: use a dedicated workqueue for cgroup bpf destruction

2024-11-08T15:26:45+00:00

[ Upstream commit 117932eea99b729ee5d12783601a4f7f5fd58a23 ]

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:
 
 __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
 

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 
Signed-off-by: Chen Ridong 
Signed-off-by: Tejun Heo 
Signed-off-by: Sasha Levin

bpf: Don't EFAULT for {g,s}setsockopt with wrong optlen

2023-07-19T14:21:05+00:00

[ Upstream commit 29ebbba7d46136cba324264e513a1e964ca16c0a ]

With the way the hooks implemented right now, we have a special
condition: optval larger than PAGE_SIZE will expose only first 4k into
BPF; any modifications to the optval are ignored. If the BPF program
doesn't handle this condition by resetting optlen to 0,
the userspace will get EFAULT.

The intention of the EFAULT was to make it apparent to the
developers that the program is doing something wrong.
However, this inadvertently might affect production workloads
with the BPF programs that are not too careful (i.e., returning EFAULT
for perfectly valid setsockopt/getsockopt calls).

Let's try to minimize the chance of BPF program screwing up userspace
by ignoring the output of those BPF programs (instead of returning
EFAULT to the userspace). pr_info_once those cases to
the dmesg to help with figuring out what's going wrong.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Suggested-by: Martin KaFai Lau 
Signed-off-by: Stanislav Fomichev 
Link: https://lore.kernel.org/r/20230511170456.1759459-2-sdf@google.com
Signed-off-by: Martin KaFai Lau 
Signed-off-by: Sasha Levin

cgroup: bpf: use cgroup_lock()/cgroup_unlock() wrappers

2023-06-21T14:00:51+00:00

[ Upstream commit 4cdb91b0dea7d7f59fa84a13c7753cd434fdedcf ]

Replace mutex_[un]lock() with cgroup_[un]lock() wrappers to stay
consistent across cgroup core and other subsystem code, while
operating on the cgroup_mutex.

Signed-off-by: Kamalesh Babulal 
Acked-by: Alexei Starovoitov 
Reviewed-by: Christian Brauner 
Signed-off-by: Tejun Heo 
Stable-dep-of: 2bd110339288 ("cgroup: always put cset in cgroup_css_set_put_fork")
Signed-off-by: Sasha Levin

bpf: Don't EFAULT for getsockopt with optval=NULL

2023-05-11T14:03:26+00:00

[ Upstream commit 00e74ae0863827d944e36e56a4ce1e77e50edb91 ]

Some socket options do getsockopt with optval=NULL to estimate the size
of the final buffer (which is returned via optlen). This breaks BPF
getsockopt assumptions about permitted optval buffer size. Let's enforce
these assumptions only when non-NULL optval is provided.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Reported-by: Martin KaFai Lau 
Signed-off-by: Stanislav Fomichev 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/ZD7Js4fj5YyI2oLd@google.com/T/#mb68daf700f87a9244a15d01d00c3f0e5b08f49f7
Link: https://lore.kernel.org/bpf/20230418225343.553806-2-sdf@google.com
Signed-off-by: Sasha Levin

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2022-10-04T00:44:18+00:00

Merge in the left-over fixes before the net-next pull-request.

Conflicts:

drivers/net/ethernet/mediatek/mtk_ppe.c
  ae3ed15da588 ("net: ethernet: mtk_eth_soc: fix state in __mtk_foe_entry_clear")
  9d8cb4c096ab ("net: ethernet: mtk_eth_soc: add foe_entry_size to mtk_eth_soc")
https://lore.kernel.org/all/6cb6893b-4921-a068-4c30-1109795110bb@tessares.net/

kernel/bpf/helpers.c
  8addbfc7b308 ("bpf: Gate dynptr API behind CAP_BPF")
  5679ff2f138f ("bpf: Move bpf_loop and bpf_for_each_map_elem under CAP_BPF")
  8a67f2de9b1d ("bpf: expose bpf_strtol and bpf_strtoul to all program types")
https://lore.kernel.org/all/20221003201957.13149-1-daniel@iogearbox.net/

Signed-off-by: Jakub Kicinski

bpf, cgroup: Reject prog_attach_flags array when effective query

2022-09-21T17:57:12+00:00

Attach flags is only valid for attached progs of this layer cgroup,
but not for effective progs. For querying with EFFECTIVE flags,
exporting attach flags does not make sense. So when effective query,
we reject prog_attach_flags array and don't need to populate it.
Also we limit attach_flags to output 0 during effective query.

Fixes: b79c9fc9551b ("bpf: implement BPF_PROG_QUERY for BPF_LSM_CGROUP")
Signed-off-by: Pu Lehui 
Link: https://lore.kernel.org/r/20220921104604.2340580-2-pulehui@huaweicloud.com
Signed-off-by: Martin KaFai Lau

Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2022-09-06T21:21:18+00:00

Daniel Borkmann says:

====================
pull-request: bpf-next 2022-09-05

The following pull-request contains BPF updates for your *net-next* tree.

We've added 106 non-merge commits during the last 18 day(s) which contain
a total of 159 files changed, 5225 insertions(+), 1358 deletions(-).

There are two small merge conflicts, resolve them as follows:

1) tools/testing/selftests/bpf/DENYLIST.s390x

  Commit 27e23836ce22 ("selftests/bpf: Add lru_bug to s390x deny list") in
  bpf tree was needed to get BPF CI green on s390x, but it conflicted with
  newly added tests on bpf-next. Resolve by adding both hunks, result:

  [...]
  lru_bug                                  # prog 'printk': failed to auto-attach: -524
  setget_sockopt                           # attach unexpected error: -524                                               (trampoline)
  cb_refs                                  # expected error message unexpected error: -524                               (trampoline)
  cgroup_hierarchical_stats                # JIT does not support calling kernel function                                (kfunc)
  htab_update                              # failed to attach: ERROR: strerror_r(-524)=22                                (trampoline)
  [...]

2) net/core/filter.c

  Commit 1227c1771dd2 ("net: Fix data-races around sysctl_[rw]mem_(max|default).")
  from net tree conflicts with commit 29003875bd5b ("bpf: Change bpf_setsockopt(SOL_SOCKET)
  to reuse sk_setsockopt()") from bpf-next tree. Take the code as it is from
  bpf-next tree, result:

  [...]
	if (getopt) {
		if (optname == SO_BINDTODEVICE)
			return -EINVAL;
		return sk_getsockopt(sk, SOL_SOCKET, optname,
				     KERNEL_SOCKPTR(optval),
				     KERNEL_SOCKPTR(optlen));
	}

	return sk_setsockopt(sk, SOL_SOCKET, optname,
			     KERNEL_SOCKPTR(optval), *optlen);
  [...]

The main changes are:

1) Add any-context BPF specific memory allocator which is useful in particular for BPF
   tracing with bonus of performance equal to full prealloc, from Alexei Starovoitov.

2) Big batch to remove duplicated code from bpf_{get,set}sockopt() helpers as an effort
   to reuse the existing core socket code as much as possible, from Martin KaFai Lau.

3) Extend BPF flow dissector for BPF programs to just augment the in-kernel dissector
   with custom logic. In other words, allow for partial replacement, from Shmulik Ladkani.

4) Add a new cgroup iterator to BPF with different traversal options, from Hao Luo.

5) Support for BPF to collect hierarchical cgroup statistics efficiently through BPF
   integration with the rstat framework, from Yosry Ahmed.

6) Support bpf_{g,s}et_retval() under more BPF cgroup hooks, from Stanislav Fomichev.

7) BPF hash table and local storages fixes under fully preemptible kernel, from Hou Tao.

8) Add various improvements to BPF selftests and libbpf for compilation with gcc BPF
   backend, from James Hilliard.

9) Fix verifier helper permissions and reference state management for synchronous
   callbacks, from Kumar Kartikeya Dwivedi.

10) Add support for BPF selftest's xskxceiver to also be used against real devices that
    support MAC loopback, from Maciej Fijalkowski.

11) Various fixes to the bpf-helpers(7) man page generation script, from Quentin Monnet.

12) Document BPF verifier's tnum_in(tnum_range(), ...) gotchas, from Shung-Hsi Yu.

13) Various minor misc improvements all over the place.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (106 commits)
  bpf: Optimize rcu_barrier usage between hash map and bpf_mem_alloc.
  bpf: Remove usage of kmem_cache from bpf_mem_cache.
  bpf: Remove prealloc-only restriction for sleepable bpf programs.
  bpf: Prepare bpf_mem_alloc to be used by sleepable bpf programs.
  bpf: Remove tracing program restriction on map types
  bpf: Convert percpu hash map to per-cpu bpf_mem_alloc.
  bpf: Add percpu allocation support to bpf_mem_alloc.
  bpf: Batch call_rcu callbacks instead of SLAB_TYPESAFE_BY_RCU.
  bpf: Adjust low/high watermarks in bpf_mem_cache
  bpf: Optimize call_rcu in non-preallocated hash map.
  bpf: Optimize element count in non-preallocated hash map.
  bpf: Relax the requirement to use preallocated hash maps in tracing progs.
  samples/bpf: Reduce syscall overhead in map_perf_test.
  selftests/bpf: Improve test coverage of test_maps
  bpf: Convert hash map to bpf_mem_alloc.
  bpf: Introduce any context BPF specific memory allocator.
  selftest/bpf: Add test for bpf_getsockopt()
  bpf: Change bpf_getsockopt(SOL_IPV6) to reuse do_ipv6_getsockopt()
  bpf: Change bpf_getsockopt(SOL_IP) to reuse do_ip_getsockopt()
  bpf: Change bpf_getsockopt(SOL_TCP) to reuse do_tcp_getsockopt()
  ...
====================

Link: https://lore.kernel.org/r/20220905161136.9150-1-daniel@iogearbox.net
Signed-off-by: Paolo Abeni

bpf: expose bpf_strtol and bpf_strtoul to all program types

2022-08-23T23:08:21+00:00

bpf_strncmp is already exposed everywhere. The motivation is to keep
those helpers in kernel/bpf/helpers.c. Otherwise it's tempting to move
them under kernel/bpf/cgroup.c because they are currently only used
by sysctl prog types.

Suggested-by: Martin KaFai Lau 
Acked-by: Martin KaFai Lau 
Signed-off-by: Stanislav Fomichev 
Link: https://lore.kernel.org/r/20220823222555.523590-4-sdf@google.com
Signed-off-by: Alexei Starovoitov

bpf: Use cgroup_{common,current}_func_proto in more hooks

2022-08-23T23:08:21+00:00

The following hooks are per-cgroup hooks but they are not
using cgroup_{common,current}_func_proto, fix it:

* BPF_PROG_TYPE_CGROUP_SKB (cg_skb)
* BPF_PROG_TYPE_CGROUP_SOCK_ADDR (cg_sock_addr)
* BPF_PROG_TYPE_CGROUP_SOCK (cg_sock)
* BPF_PROG_TYPE_LSM+BPF_LSM_CGROUP

Also:

* move common func_proto's into cgroup func_proto handlers
* make sure bpf_{g,s}et_retval are not accessible from recvmsg,
  getpeername and getsockname (return/errno is ignored in these
  places)
* as a side effect, expose get_current_pid_tgid, get_current_comm_proto,
  get_current_ancestor_cgroup_id, get_cgroup_classid to more cgroup
  hooks

Acked-by: Martin KaFai Lau 
Signed-off-by: Stanislav Fomichev 
Link: https://lore.kernel.org/r/20220823222555.523590-3-sdf@google.com
Signed-off-by: Alexei Starovoitov