In the Linux kernel, the following vulnerability has been resolved:
netfilter: conntrack: serialize hash resizes and cleanups
Syzbot was able to trigger the following warning [1]
No repro found by syzbot yet but I was able to trigger similar issue
by having 2 scripts running in parallel, changing conntrack hash sizes,
and:
for j in `seq 1 1000` ; do unshare -n /bin/true >/dev/null ; done
It would take more than 5 minutes for net_namespace structures
to be cleaned up.
This is because nf_ct_iterate_cleanup() has to restart everytime
a resize happened.
By adding a mutex, we can serialize hash resizes and cleanups
and also make get_next_corpse() faster by skipping over empty
buckets.
Even without resizes in the picture, this patch considerably
speeds up network namespace dismantles.
[1]
INFO: task syz-executor.0:8312 can't die for more than 144 seconds.
task:syz-executor.0 state:R running task stack:25672 pid: 8312 ppid: 6573 flags:0x00004006
Call Trace:
context_switch kernel/sched/core.c:4955 [inline]
__schedule+0x940/0x26f0 kernel/sched/core.c:6236
preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6408
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
__local_bh_enable_ip+0x109/0x120 kernel/softirq.c:390
local_bh_enable include/linux/bottom_half.h:32 [inline]
get_next_corpse net/netfilter/nf_conntrack_core.c:2252 [inline]
nf_ct_iterate_cleanup+0x15a/0x450 net/netfilter/nf_conntrack_core.c:2275
nf_conntrack_cleanup_net_list+0x14c/0x4f0 net/netfilter/nf_conntrack_core.c:2469
ops_exit_list+0x10d/0x160 net/core/net_namespace.c:171
setup_net+0x639/0xa30 net/core/net_namespace.c:349
copy_net_ns+0x319/0x760 net/core/net_namespace.c:470
create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
ksys_unshare+0x445/0x920 kernel/fork.c:3128
__do_sys_unshare kernel/fork.c:3202 [inline]
__se_sys_unshare kernel/fork.c:3200 [inline]
__x64_sys_unshare+0x2d/0x40 kernel/fork.c:3200
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f63da68e739
RSP: 002b:00007f63d7c05188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f63da792f80 RCX: 00007f63da68e739
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007f63da6e8cc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f63da792f80
R13: 00007fff50b75d3f R14: 00007f63d7c05300 R15: 0000000000022000
Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8b980020 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
2 locks held by kworker/u4:2/153:
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
#1: ffffc9000140fdb0 ((kfence_timer).work){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
1 lock held by systemd-udevd/2970:
1 lock held by in:imklog/6258:
#0: ffff88807f970ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
3 locks held by kworker/1:6/8158:
1 lock held by syz-executor.0/8312:
2 locks held by kworker/u4:13/9320:
1 lock held by
---truncated---
netfilter: conntrack: serialize hash resizes and cleanups
Syzbot was able to trigger the following warning [1]
No repro found by syzbot yet but I was able to trigger similar issue
by having 2 scripts running in parallel, changing conntrack hash sizes,
and:
for j in `seq 1 1000` ; do unshare -n /bin/true >/dev/null ; done
It would take more than 5 minutes for net_namespace structures
to be cleaned up.
This is because nf_ct_iterate_cleanup() has to restart everytime
a resize happened.
By adding a mutex, we can serialize hash resizes and cleanups
and also make get_next_corpse() faster by skipping over empty
buckets.
Even without resizes in the picture, this patch considerably
speeds up network namespace dismantles.
[1]
INFO: task syz-executor.0:8312 can't die for more than 144 seconds.
task:syz-executor.0 state:R running task stack:25672 pid: 8312 ppid: 6573 flags:0x00004006
Call Trace:
context_switch kernel/sched/core.c:4955 [inline]
__schedule+0x940/0x26f0 kernel/sched/core.c:6236
preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6408
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
__local_bh_enable_ip+0x109/0x120 kernel/softirq.c:390
local_bh_enable include/linux/bottom_half.h:32 [inline]
get_next_corpse net/netfilter/nf_conntrack_core.c:2252 [inline]
nf_ct_iterate_cleanup+0x15a/0x450 net/netfilter/nf_conntrack_core.c:2275
nf_conntrack_cleanup_net_list+0x14c/0x4f0 net/netfilter/nf_conntrack_core.c:2469
ops_exit_list+0x10d/0x160 net/core/net_namespace.c:171
setup_net+0x639/0xa30 net/core/net_namespace.c:349
copy_net_ns+0x319/0x760 net/core/net_namespace.c:470
create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
ksys_unshare+0x445/0x920 kernel/fork.c:3128
__do_sys_unshare kernel/fork.c:3202 [inline]
__se_sys_unshare kernel/fork.c:3200 [inline]
__x64_sys_unshare+0x2d/0x40 kernel/fork.c:3200
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f63da68e739
RSP: 002b:00007f63d7c05188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f63da792f80 RCX: 00007f63da68e739
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007f63da6e8cc4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f63da792f80
R13: 00007fff50b75d3f R14: 00007f63d7c05300 R15: 0000000000022000
Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8b980020 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
2 locks held by kworker/u4:2/153:
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]
#0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268
#1: ffffc9000140fdb0 ((kfence_timer).work){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272
1 lock held by systemd-udevd/2970:
1 lock held by in:imklog/6258:
#0: ffff88807f970ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990
3 locks held by kworker/1:6/8158:
1 lock held by syz-executor.0/8312:
2 locks held by kworker/u4:13/9320:
1 lock held by
---truncated---
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
Configuration 1 [-]
|
| Package | CPE | Advisory | Released Date |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | |||
| kernel-rt-0:4.18.0-553.16.1.rt7.357.el8_10 | cpe:/a:redhat:enterprise_linux:8::nfv | RHSA-2024:5102 | 2024-08-08T00:00:00Z |
| kernel-0:4.18.0-553.16.1.el8_10 | cpe:/o:redhat:enterprise_linux:8 | RHSA-2024:5101 | 2024-08-08T00:00:00Z |
No data.
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 25 Sep 2025 15:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Linux
Linux linux Kernel |
|
| Weaknesses | NVD-CWE-noinfo | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:* |
|
| Vendors & Products |
Linux
Linux linux Kernel |
Fri, 01 Nov 2024 15:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
|
Thu, 08 Aug 2024 19:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Redhat
Redhat enterprise Linux |
|
| CPEs | cpe:/a:redhat:enterprise_linux:8::nfv cpe:/o:redhat:enterprise_linux:8 |
|
| Vendors & Products |
Redhat
Redhat enterprise Linux |
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-12-18T11:37:27.872Z
Reserved: 2024-05-21T14:58:30.817Z
Link: CVE-2021-47408
Vulnrichment
Updated: 2024-08-04T05:39:59.320Z
NVD
Status : Analyzed
Published: 2024-05-21T15:15:26.337
Modified: 2025-09-25T15:32:02.877
Link: CVE-2021-47408
Redhat
OpenCVE Enrichment
No data.
Weaknesses