# CVE-2021-47041: nvmet-tcp: fix incorrect locking in state_change sk callback > A locking error in the Linux kernel's nvmet-tcp module causes a deadlock, leading to a denial of service when host and controller run on the same system. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 28 Feb 2024 - **Updated:** 5 Aug 2026 - **Also known as:** DEBIAN-CVE-2021-47041, GHSA-cpr5-fxjg-jcr6, UBUNTU-CVE-2021-47041 ## What is CVE-2021-47041? CVE-2021-47041 is a high-severity vulnerability in Linux kernel, published on 28 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: nvmet-tcp: fix incorrect locking in state_change sk callback We are not changing anything in the TCP connection state so we should not take a write_lock but rather a read lock. This caused a deadlock when running nvmet-tcp and nvme-tcp on the same system, where state_change callbacks on the host and on the controller side have causal relationship and made lockdep report on this with blktests: ================================ WARNING: inconsistent lock state 5.12.0-rc3 #1 Tainted: G I -------------------------------- inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-R} usage. nvme/1324 [HC0[0]:SC0[0]:HE1:SE1] takes: ffff888363151000 (clock-AF_INET){++-?}-{2:2}, at: nvme_tcp_state_change+0x21/0x150 [nvme_tcp] {IN-SOFTIRQ-W} state was registered at: __lock_acquire+0x79b/0x18d0 lock_acquire+0x1ca/0x480 _raw_write_lock_bh+0x39/0x80 nvmet_tcp_state_change+0x21/0x170 [nvmet_tcp] tcp_fin+0x2a8/0x780 tcp_data_queue+0xf94/0x1f20 tcp_rcv_established+0x6ba/0x1f00 tcp_v4_do_rcv+0x502/0x760 tcp_v4_rcv+0x257e/0x3430 ip_protocol_deliver_rcu+0x69/0x6a0 ip_local_deliver_finish+0x1e2/0x2f0 ip_local_deliver+0x1a2/0x420 ip_rcv+0x4fb/0x6b0 __netif_receive_skb_one_core+0x162/0x1b0 process_backlog+0x1ff/0x770 __napi_poll.constprop.0+0xa9/0x5c0 net_rx_action+0x7b3/0xb30 __do_softirq+0x1f0/0x940 do_softirq+0xa1/0xd0 __local_bh_enable_ip+0xd8/0x100 ip_finish_output2+0x6b7/0x18a0 __ip_queue_xmit+0x706/0x1aa0 __tcp_transmit_skb+0x2068/0x2e20 tcp_write_xmit+0xc9e/0x2bb0 __tcp_push_pending_frames+0x92/0x310 inet_shutdown+0x158/0x300 __nvme_tcp_stop_queue+0x36/0x270 [nvme_tcp] nvme_tcp_stop_queue+0x87/0xb0 [nvme_tcp] nvme_tcp_teardown_admin_queue+0x69/0xe0 [nvme_tcp] nvme_do_delete_ctrl+0x100/0x10c [nvme_core] nvme_sysfs_delete.cold+0x8/0xd [nvme_core] kernfs_fop_write_iter+0x2c7/0x460 new_sync_write+0x36c/0x610 vfs_write+0x5c0/0x870 ksys_write+0xf9/0x1d0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae irq event stamp: 10687 hardirqs last enabled at (10687): [] _raw_spin_unlock_irqrestore+0x2d/0x40 hardirqs last disabled at (10686): [] _raw_spin_lock_irqsave+0x68/0x90 softirqs last enabled at (10684): [] __do_softirq+0x608/0x940 softirqs last disabled at (10649): [] do_softirq+0xa1/0xd0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(clock-AF_INET); lock(clock-AF_INET); *** DEADLOCK *** 5 locks held by nvme/1324: #0: ffff8884a01fe470 (sb_writers#4){.+.+}-{0:0}, at: ksys_write+0xf9/0x1d0 #1: ffff8886e435c090 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x216/0x460 #2: ffff888104d90c38 (kn->active#255){++++}-{0:0}, at: kernfs_remove_self+0x22d/0x330 #3: ffff8884634538d0 (&queue->queue_lock){+.+.}-{3:3}, at: nvme_tcp_stop_queue+0x52/0xb0 [nvme_tcp] #4: ffff888363150d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_shutdown+0x59/0x300 stack backtrace: CPU: 26 PID: 1324 Comm: nvme Tainted: G I 5.12.0-rc3 #1 Hardware name: Dell Inc. PowerEdge R640/06NR82, BIOS 2.10.0 11/12/2020 Call Trace: dump_stack+0x93/0xc2 mark_lock_irq.cold+0x2c/0xb3 ? verify_lock_unused+0x390/0x390 ? stack_trace_consume_entry+0x160/0x160 ? lock_downgrade+0x100/0x100 ? save_trace+0x88/0x5e0 ? _raw_spin_unlock_irqrestore+0x2d/0x40 mark_lock+0x530/0x1470 ? mark_lock_irq+0x1d10/0x1d10 ? enqueue_timer+0x660/0x660 mark_usage+0x215/0x2a0 __lock_acquire+0x79b/0x18d0 ? tcp_schedule_loss_probe.part.0+0x38c/0x520 lock_acquire+0x1ca/0x480 ? nvme_tcp_state_change+0x21/0x150 [nvme_tcp] ? rcu_read_unlock+0x40/0x40 ? tcp_mtu_probe+0x1ae0/0x1ae0 ? kmalloc_reserve+0xa0/0xa0 ? sysfs_file_ops+0x170/0x170 _raw_read_lock+0x3d/0xa0 ? nvme_tcp_state_change+0x21/0x150 [nvme_tcp] nvme_tcp_state_change+0x21/0x150 [nvme_tcp] ? sysfs_file_ops ---truncated--- Weakness: CWE-667 (Improper Locking) ## Which versions are affected by CVE-2021-47041? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2021-47041? Apply the vendor's patch. ## Is CVE-2021-47041 being exploited? There is no known exploitation of CVE-2021-47041 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-47041 and fix it if it is affected. What it is: CVE-2021-47041 is a high-severity vulnerability in Linux kernel, published on 28 Feb 2024. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-47041 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-47041/ (Markdown: https://insights.sbomify.com/CVE-2021-47041/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47041 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47041 - OSV: https://osv.dev/vulnerability/CVE-2021-47041 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-47041/ Summaries are generated and may contain mistakes; the official description above is the record.