Re: [PATCH RFC 4/4] fs: allow mknod in non-initial userns using cgroup device guard

[kernel test robot]

Hello,

kernel test robot noticed "WARNING:suspicious_RCU_usage" on:

commit: bffc333633f1e681c01ada11bd695aa220518bd8 ("[PATCH RFC 4/4] fs: allow mknod in non-initial userns using cgroup device guard")
url: https://github.com/intel-lab-lkp/linux/commits/Michael-Wei/bpf-add-cgroup-device-guard-to-flag-a-cgroup-device-prog/20230814-224110
patch link: https://lore.kernel.org/all/20230814-devcg_guard-v1-4-654971ab88b1@xxxxxxxxxxxxxxxxxxx/
patch subject: [PATCH RFC 4/4] fs: allow mknod in non-initial userns using cgroup device guard

in testcase: boot

compiler: gcc-12
test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G

(please refer to attached dmesg/kmsg for entire log/backtrace)



If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-lkp/202308151506.6be3b169-oliver.sang@xxxxxxxxx



[   14.468719][  T139]
[   14.468999][  T139] =============================
[   14.469545][  T139] WARNING: suspicious RCU usage
[   14.469968][  T139] 6.5.0-rc6-00004-gbffc333633f1 #1 Not tainted
[   14.470520][  T139] -----------------------------
[   14.470940][  T139] include/linux/cgroup.h:423 suspicious rcu_dereference_check() usage!
[   14.471703][  T139]
[   14.471703][  T139] other info that might help us debug this:
[   14.471703][  T139]
[   14.472692][  T139]
[   14.472692][  T139] rcu_scheduler_active = 2, debug_locks = 1
[   14.473469][  T139] no locks held by (journald)/139.
[   14.473935][  T139]
[   14.473935][  T139] stack backtrace:
[   14.474454][  T139] CPU: 1 PID: 139 Comm: (journald) Not tainted 6.5.0-rc6-00004-gbffc333633f1 #1
[   14.475296][  T139] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[   14.476298][  T139] Call Trace:
[   14.476608][  T139]  dump_stack_lvl+0x78/0x8c
[   14.477055][  T139]  dump_stack+0x12/0x18
[   14.477420][  T139]  lockdep_rcu_suspicious+0x153/0x1a4
[   14.477928][  T139]  cgroup_bpf_device_guard_enabled+0x14f/0x168
[   14.478476][  T139]  devcgroup_task_is_guarded+0x10/0x20
[   14.478973][  T139]  may_open_dev+0x11/0x44
[   14.479367][  T139]  may_open+0x115/0x13c
[   14.479727][  T139]  do_open+0xa1/0x378
[   14.480113][  T139]  path_openat+0xdc/0x1bc
[   14.480512][  T139]  do_filp_open+0x91/0x124
[   14.480911][  T139]  ? lock_release+0x62/0x118
[   14.481329][  T139]  ? _raw_spin_unlock+0x18/0x34
[   14.481797][  T139]  ? alloc_fd+0x112/0x1c4
[   14.482183][  T139]  do_sys_openat2+0x7a/0xa0
[   14.482592][  T139]  __ia32_sys_openat+0x66/0x9c
[   14.483065][  T139]  do_int80_syscall_32+0x27/0x48
[   14.483502][  T139]  entry_INT80_32+0x10d/0x10d
[   14.483962][  T139] EIP: 0xa7f39092
[   14.484267][  T139] Code: 00 00 00 e9 90 ff ff ff ff a3 24 00 00 00 68 30 00 00 00 e9 80 ff ff ff ff a3 f8 ff ff ff 66 90 00 00 00 00 00 00 00 00 cd 80 <c3> 8d b4
 26 00 00 00 00 8d b6 00 00 00 00 8b 1c 24 c3 8d b4 26 00
[   14.485995][  T139] EAX: ffffffda EBX: ffffff9c ECX: 005df542 EDX: 00008100
[   14.486622][  T139] ESI: 00000000 EDI: 00000000 EBP: affeb888 ESP: affeb6ec
[   14.487225][  T139] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00200246



The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20230815/202308151506.6be3b169-oliver.sang@xxxxxxxxx



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