CVE-2021-47408 (GCVE-0-2021-47408)

Vulnerability from cvelistv5 – Published: 2024-05-21 15:04 – Updated: 2025-12-18 11:37
VLAI?
Title
netfilter: conntrack: serialize hash resizes and cleanups
Summary
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---
Severity ?
4.7 (Medium)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 0d02d5646eb84403766a11a1d3b19e670a3d45d5 , < e2d192301a0df8160d1555b66ae8611e8050e424 (git)
Affected: 0d02d5646eb84403766a11a1d3b19e670a3d45d5 , < 7ea6f5848281182ce0cff6cafdcf3fbdeb8ca7e1 (git)
Affected: 0d02d5646eb84403766a11a1d3b19e670a3d45d5 , < e9edc188fc76499b0b9bd60364084037f6d03773 (git)
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    Linux Linux Affected: 4.13
Unaffected: 0 , < 4.13 (semver)
Unaffected: 5.10.71 , ≤ 5.10.* (semver)
Unaffected: 5.14.10 , ≤ 5.14.* (semver)
Unaffected: 5.15 , ≤ * (original_commit_for_fix)
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    "vulnrichment": {
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do unshare -n /bin/true \u003e/dev/null ; done\\n\\nIt would take more than 5 minutes for net_namespace structures\\nto be cleaned up.\\n\\nThis is because nf_ct_iterate_cleanup() has to restart everytime\\na resize happened.\\n\\nBy adding a mutex, we can serialize hash resizes and cleanups\\nand also make get_next_corpse() faster by skipping over empty\\nbuckets.\\n\\nEven without resizes in the picture, this patch considerably\\nspeeds up network namespace dismantles.\\n\\n[1]\\nINFO: task syz-executor.0:8312 can\u0027t die for more than 144 seconds.\\ntask:syz-executor.0  state:R  running task     stack:25672 pid: 8312 ppid:  6573 flags:0x00004006\\nCall Trace:\\n context_switch kernel/sched/core.c:4955 [inline]\\n __schedule+0x940/0x26f0 kernel/sched/core.c:6236\\n preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6408\\n preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35\\n __local_bh_enable_ip+0x109/0x120 kernel/softirq.c:390\\n local_bh_enable include/linux/bottom_half.h:32 [inline]\\n get_next_corpse net/netfilter/nf_conntrack_core.c:2252 [inline]\\n nf_ct_iterate_cleanup+0x15a/0x450 net/netfilter/nf_conntrack_core.c:2275\\n nf_conntrack_cleanup_net_list+0x14c/0x4f0 net/netfilter/nf_conntrack_core.c:2469\\n ops_exit_list+0x10d/0x160 net/core/net_namespace.c:171\\n setup_net+0x639/0xa30 net/core/net_namespace.c:349\\n copy_net_ns+0x319/0x760 net/core/net_namespace.c:470\\n create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110\\n unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226\\n ksys_unshare+0x445/0x920 kernel/fork.c:3128\\n __do_sys_unshare kernel/fork.c:3202 [inline]\\n __se_sys_unshare kernel/fork.c:3200 [inline]\\n __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3200\\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\\n do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80\\n entry_SYSCALL_64_after_hwframe+0x44/0xae\\nRIP: 0033:0x7f63da68e739\\nRSP: 002b:00007f63d7c05188 EFLAGS: 00000246 ORIG_RAX: 0000000000000110\\nRAX: ffffffffffffffda RBX: 00007f63da792f80 RCX: 00007f63da68e739\\nRDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000\\nRBP: 00007f63da6e8cc4 R08: 0000000000000000 R09: 0000000000000000\\nR10: 0000000000000000 R11: 0000000000000246 R12: 00007f63da792f80\\nR13: 00007fff50b75d3f R14: 00007f63d7c05300 R15: 0000000000022000\\n\\nShowing all locks held in the system:\\n1 lock held by khungtaskd/27:\\n #0: ffffffff8b980020 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446\\n2 locks held by kworker/u4:2/153:\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1198 [inline]\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:634 [inline]\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:661 [inline]\\n #0: ffff888010c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x896/0x1690 kernel/workqueue.c:2268\\n #1: ffffc9000140fdb0 ((kfence_timer).work){+.+.}-{0:0}, at: process_one_work+0x8ca/0x1690 kernel/workqueue.c:2272\\n1 lock held by systemd-udevd/2970:\\n1 lock held by in:imklog/6258:\\n #0: ffff88807f970ff0 (\u0026f-\u003ef_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:990\\n3 locks held by kworker/1:6/8158:\\n1 lock held by syz-executor.0/8312:\\n2 locks held by kworker/u4:13/9320:\\n1 lock held by\\n---truncated---\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.71\", \"versionStartIncluding\": \"4.13\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.14.10\", \"versionStartIncluding\": \"4.13\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15\", \"versionStartIncluding\": \"4.13\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-12-18T11:37:27.872Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47408\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-12-18T11:37:27.872Z\", \"dateReserved\": \"2024-05-21T14:58:30.817Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-21T15:04:00.651Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.