[syzbot] [kernel?] INFO: task hung in rxrpc_destroy_all_connections (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7dff99b35460 Remove WARN_ALL_UNSEEDED_RANDOM kernel config..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10ae4202580000
kernel config: https://syzkaller.appspot.com/x/.config?x=af6ed0125ed44356
dashboard link: https://syzkaller.appspot.com/bug?extid=138f5aa6fa94d4802887
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/45c7b6686727/disk-7dff99b3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/36fcc9cd6296/vmlinux-7dff99b3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fe952fd2745b/bzImage-7dff99b3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+138f5a...@syzkaller.appspotmail.com

INFO: task kworker/u8:0:12022 blocked for more than 143 seconds.
Tainted: G U L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:0 state:D stack:23528 pid:12022 tgid:12022 ppid:2 task_flags:0x4208160 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0xfee/0x60e0 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7004
schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
__flush_workqueue+0x3f7/0x1200 kernel/workqueue.c:4083
rxrpc_destroy_all_connections+0xf9/0x420 net/rxrpc/conn_object.c:477
rxrpc_exit_net+0x7b/0xc0 net/rxrpc/net_ns.c:113
ops_exit_list net/core/net_namespace.c:199 [inline]
ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
cleanup_net+0x499/0x920 net/core/net_namespace.c:704
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
kthread+0x370/0x450 kernel/kthread.c:467
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
INFO: task syz.8.2467:17905 blocked for more than 144 seconds.
Tainted: G U L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.2467 state:D stack:25112 pid:17905 tgid:17904 ppid:17004 task_flags:0x400140 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5295 [inline]
__schedule+0xfee/0x60e0 kernel/sched/core.c:6907
__schedule_loop kernel/sched/core.c:6989 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7004
schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
__flush_workqueue+0x3f7/0x1200 kernel/workqueue.c:4083
rxrpc_destroy_all_locals+0x3e/0x190 net/rxrpc/local_object.c:475
rxrpc_exit_net+0x8b/0xc0 net/rxrpc/net_ns.c:115
ops_exit_list net/core/net_namespace.c:199 [inline]
ops_undo_list+0x2ee/0xab0 net/core/net_namespace.c:252
setup_net+0x1fa/0x3a0 net/core/net_namespace.c:462
copy_net_ns+0x46f/0x7c0 net/core/net_namespace.c:581
create_new_namespaces+0x3ea/0xac0 kernel/nsproxy.c:130
unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:226
ksys_unshare+0x455/0xab0 kernel/fork.c:3174
__do_sys_unshare kernel/fork.c:3245 [inline]
__se_sys_unshare kernel/fork.c:3243 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:3243
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2eed39c629
RSP: 002b:00007f2eee32c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f2eed615fa0 RCX: 00007f2eed39c629
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000080
RBP: 00007f2eed432b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2eed616038 R14: 00007f2eed615fa0 R15: 00007ffca313eaa8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
#0: ffffffff8e7e9220 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#0: ffffffff8e7e9220 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#0: ffffffff8e7e9220 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/7330:
#0: ffff8880393580a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc900035fd2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
3 locks held by kworker/u8:0/12022:
#0: ffff88801c6ae948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250
#1: ffffc900038a7d08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251
#2: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:675
1 lock held by syz.8.2467/17905:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
1 lock held by syz.7.2554/18277:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
1 lock held by syz.6.2559/18314:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
1 lock held by syz.9.2571/18373:
#0: ffff8880781f9348 (&sb->s_type->i_mutex_key#14){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline]
#0: ffff8880781f9348 (&sb->s_type->i_mutex_key#14){+.+.}-{4:4}, at: __sock_release+0x86/0x260 net/socket.c:661
1 lock held by syz.0.2623/18776:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
1 lock held by syz.3.2744/19524:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
1 lock held by syz.2.2835/20011:
#0: ffffffff905f95d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
2 locks held by syz.1.2847/20056:

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Tainted: G U L syzkaller #0 PREEMPT(full)
Tainted: [U]=USER, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x141/0x190 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
watchdog+0xd25/0x1050 kernel/hung_task.c:515
kthread+0x370/0x450 kernel/kthread.c:467
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


---
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[Roberto A. Foglietta]

> On Wednesday, 25 February 2026 at 08:45:32 UTC+1 syzbot wrote:
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit: 7dff99b35460 Remove WARN_ALL_UNSEEDED_RANDOM kernel config..
> git tree: upstream

[...]

> On Fri, 20 Feb 2026 at 01:20, Roberto A. Foglietta <roberto.foglietta at gmail.com> wrote:

http://lists.landley.net/pipermail/toybox-landley.net/2026-February/030915.html

Issue replicated here using 5.15.201 (LTS):

https://github.com/robang74/bare-minimal-linux-system/commit/9a91bd6be3d087bcf762a294072c934f1bfc29f7

The main problem is not polluting the dmesg (that option is inactive by default) but the underlying problem of subsystem that need secure cryptographic seeding when the kernel pool has nothing to offer. The root of the problem is waiting that events happens for collecting entropy (what is "entropy"? data after collection, but before collection?) instead of generating "chaos" to create it (thermodynamics law in phisics grant that doing a work L part of the energy is converted in work (ordinated movements) and part in entropy (disordinated movements) and the Lorenz strange attractors theory (or the Theory of the Chaos, or the 3-body problem or the billiard 7-cushion uncertanty) grant that a deterministic system can for sure generate randomness without loosing the macroscopic ordinated local determinism. In C-language code:

https://github.com/robang74/working-in-progress/blob/main/prpr/prpr.c

History in kernel commits by search that specific text:

+:git-shell:master:linux-kernel> search "cryptographically secure random numbers"
7dff99b35460 HEAD (HEAD -> master, origin/master, origin/HEAD, linux/master) Remove WARN_ALL_UNSEEDED_RANDOM kernel config option
2b7a25df823d HEAD (grafted, stable/master) Merge tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
950a81224e8b HEAD lib/crypto: tests: Add hash-test-template.h and gen-hash-testvecs.py
e9bc360b105c HEAD fault-inject: use prandom where cryptographically secure randomness is not needed
f900fde28883 HEAD crypto: testmgr - fix RNG performance in fuzz tests
9a47249d444d HEAD random: Make crng state queryable
d06bfd1989fe HEAD random: warn when kernel uses unseeded randomness
e297a783e415 HEAD random: add wait_for_random_bytes() API

Best regards, R-

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.