[syzbot] [net?] WARNING: suspicious RCU usage in task_cls_state

[syzbot] [net?] WARNING: suspicious RCU usage in task_cls_state

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    079e5c56a5c4 bpf: Fix error return value in bpf_copy_from_..
git tree:       bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=178ae170580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c6c517d2f439239
dashboard link: https://syzkaller.appspot.com/bug?extid=b4169a1cfb945d2ed0ec
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13bc35f4580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15f195f4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8d7d35d067bc/disk-079e5c56.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74d2648ea7f4/vmlinux-079e5c56.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e751e253ee4f/bzImage-079e5c56.xz

The issue was bisected to:

commit ee971630f20fd421fffcdc4543731ebcb54ed6d0
Author: Feng Yang <yangfeng@kylinos.cn>
Date:   Tue May 6 06:14:33 2025 +0000

    bpf: Allow some trace helpers for all prog types

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14cd68e8580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=16cd68e8580000
console output: https://syzkaller.appspot.com/x/log.txt?x=12cd68e8580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com
Fixes: ee971630f20f ("bpf: Allow some trace helpers for all prog types")

=============================
WARNING: suspicious RCU usage
6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 Not tainted
-----------------------------
net/core/netclassid_cgroup.c:24 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor296/5833:
 #0: ffffffff8df3ba40 (rcu_read_lock_trace){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8df3ba40 (rcu_read_lock_trace){....}-{0:0}, at: rcu_read_lock_trace+0x38/0x80 include/linux/rcupdate_trace.h:58

stack backtrace:
CPU: 0 UID: 0 PID: 5833 Comm: syz-executor296 Not tainted 6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x140/0x1d0 kernel/locking/lockdep.c:6865
 task_cls_state+0x1a5/0x1d0 net/core/netclassid_cgroup.c:23
 __task_get_classid include/net/cls_cgroup.h:50 [inline]
 ____bpf_get_cgroup_classid_curr net/core/filter.c:3086 [inline]
 bpf_get_cgroup_classid_curr+0x18/0x60 net/core/filter.c:3084
 bpf_prog_83da9cb0e78d4768+0x2c/0x5a
 bpf_dispatcher_nop_func include/linux/bpf.h:1322 [inline]
 __bpf_prog_run include/linux/filter.h:718 [inline]
 bpf_prog_run include/linux/filter.h:725 [inline]
 bpf_prog_run_pin_on_cpu+0x67/0x150 include/linux/filter.h:742
 bpf_prog_test_run_syscall+0x312/0x4b0 net/bpf/test_run.c:1564
 bpf_prog_test_run+0x2a9/0x340 kernel/bpf/syscall.c:4429
 __sys_bpf+0x4a4/0x860 kernel/bpf/syscall.c:5854
 __do_sys_bpf kernel/bpf/syscall.c:5943 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5941 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5941
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fda75b18a69
Code: d8 5b c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdd0546d48 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fda75b18a69
RDX: 0000000000000048 RSI: 0000200000000500 RDI: 000000000000000a


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
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#syz undup

Re: [syzbot] [net?] WARNING: suspicious RCU usage in task_cls_state

[Charalampos Mitrodimas]

syzbot <syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com> writes:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    079e5c56a5c4 bpf: Fix error return value in bpf_copy_from_..
> git tree:       bpf-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=178ae170580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c6c517d2f439239
> dashboard link: https://syzkaller.appspot.com/bug?extid=b4169a1cfb945d2ed0ec
> compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13bc35f4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15f195f4580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/8d7d35d067bc/disk-079e5c56.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/74d2648ea7f4/vmlinux-079e5c56.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e751e253ee4f/bzImage-079e5c56.xz
>
> The issue was bisected to:
>
> commit ee971630f20fd421fffcdc4543731ebcb54ed6d0
> Author: Feng Yang <yangfeng@kylinos.cn>
> Date:   Tue May 6 06:14:33 2025 +0000
>
>     bpf: Allow some trace helpers for all prog types
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14cd68e8580000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=16cd68e8580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12cd68e8580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com
> Fixes: ee971630f20f ("bpf: Allow some trace helpers for all prog types")
>
> =============================
> WARNING: suspicious RCU usage
> 6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 Not tainted
> -----------------------------
> net/core/netclassid_cgroup.c:24 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by syz-executor296/5833:
>  #0: ffffffff8df3ba40 (rcu_read_lock_trace){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
>  #0: ffffffff8df3ba40 (rcu_read_lock_trace){....}-{0:0}, at: rcu_read_lock_trace+0x38/0x80 include/linux/rcupdate_trace.h:58
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 5833 Comm: syz-executor296 Not tainted 6.15.0-rc4-syzkaller-g079e5c56a5c4 #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>  lockdep_rcu_suspicious+0x140/0x1d0 kernel/locking/lockdep.c:6865
>  task_cls_state+0x1a5/0x1d0 net/core/netclassid_cgroup.c:23
>  __task_get_classid include/net/cls_cgroup.h:50 [inline]
>  ____bpf_get_cgroup_classid_curr net/core/filter.c:3086 [inline]
>  bpf_get_cgroup_classid_curr+0x18/0x60 net/core/filter.c:3084
>  bpf_prog_83da9cb0e78d4768+0x2c/0x5a
>  bpf_dispatcher_nop_func include/linux/bpf.h:1322 [inline]
>  __bpf_prog_run include/linux/filter.h:718 [inline]
>  bpf_prog_run include/linux/filter.h:725 [inline]
>  bpf_prog_run_pin_on_cpu+0x67/0x150 include/linux/filter.h:742
>  bpf_prog_test_run_syscall+0x312/0x4b0 net/bpf/test_run.c:1564
>  bpf_prog_test_run+0x2a9/0x340 kernel/bpf/syscall.c:4429
>  __sys_bpf+0x4a4/0x860 kernel/bpf/syscall.c:5854
>  __do_sys_bpf kernel/bpf/syscall.c:5943 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5941 [inline]
>  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5941
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fda75b18a69
> Code: d8 5b c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffdd0546d48 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fda75b18a69
> RDX: 0000000000000048 RSI: 0000200000000500 RDI: 000000000000000a
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

#syz test: https://github.com/charmitro/linux.git e5c42d49bfb967c3c35f536971f397492d2f46bf

Re: [syzbot] [net?] WARNING: suspicious RCU usage in task_cls_state

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com
Tested-by: syzbot+b4169a1cfb945d2ed0ec@syzkaller.appspotmail.com

Tested on:

commit:         e5c42d49 net: Fix RCU warning in task_cls_state for BP..
git tree:       https://github.com/charmitro/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=12750a0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c6c517d2f439239
dashboard link: https://syzkaller.appspot.com/bug?extid=b4169a1cfb945d2ed0ec
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.