CVE-2021-4454can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate
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In the Linux kernel, the following vulnerability has been resolved: can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate The conclusion "j1939_session_deactivate() should be called with a session ref-count of at least 2" is incorrect. In some concurrent scenarios, j1939_session_deactivate can be called with the session ref-count less than 2. But there is not any problem because it will check the session active state before session putting in j1939_session_deactivate_locked(). Here is the concurrent scenario of the problem reported by syzbot and my reproduction log. cpu0 cpu1 j1939_xtp_rx_eoma j1939_xtp_rx_abort_one j1939_session_get_by_addr [kref == 2] j1939_session_get_by_addr [kref == 3] j1939_session_deactivate [kref == 2] j1939_session_put [kref == 1] j1939_session_completed j1939_session_deactivate WARN_ON_ONCE(kref < 2) ===================================================== WARNING: CPU: 1 PID: 21 at net/can/j1939/transport.c:1088 j1939_session_deactivate+0x5f/0x70 CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.14.0-rc7+ #32 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 RIP: 0010:j1939_session_deactivate+0x5f/0x70 Call Trace: j1939_session_deactivate_activate_next+0x11/0x28 j1939_xtp_rx_eoma+0x12a/0x180 j1939_tp_recv+0x4a2/0x510 j1939_can_recv+0x226/0x380 can_rcv_filter+0xf8/0x220 can_receive+0x102/0x220 ? process_backlog+0xf0/0x2c0 can_rcv+0x53/0xf0 __netif_receive_skb_one_core+0x67/0x90 ? process_backlog+0x97/0x2c0 __netif_receive_skb+0x22/0x80
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 15, 2026
Affected products
Linux Linux linux:linux (from the name) | from 7eef18c0479ba5d9f54fba30cd77c233ebca3eb1 before 6950df42a03c9ac9290503ced3f371199cb68fa9; from 55dd22c5d029423f513fd849e633adf0e9c10d0c before b6d44072117bba057d50f7a2f96e5d070c65926d; from 0c71437dd50dd687c15d8ca80b3b68f10bb21d63 before 9ab896775f98ff54b68512f345eed178bf961084; from 0c71437dd50dd687c15d8ca80b3b68f10bb21d63 before 1740a1e45eee65099a92fb502e1e67e63aad277d; from 0c71437dd50dd687c15d8ca80b3b68f10bb21d63 before d0553680f94c49bbe0e39eb50d033ba563b4212d; 5e1fc537c1be332aef9621ca9146aeb3ba59522f; from 5.4.138 before 5.4.232; from 5.10.56 before 5.10.168; and 1 more ranges | CNA record |
linux linux_kernel linux:linux_kernel | from 5.4.138 before 5.4.232; from 5.10.56 before 5.10.168; from 5.13.8 before 5.14; from 5.14.1 before 5.15.93; from 5.16 before 6.1.11; 5.14; 5.14; 5.14; and 8 more ranges | NVD |
References
- https://git.kernel.org/stable/c/6950df42a03c9ac9290503ced3f371199cb68fa9patch
- https://git.kernel.org/stable/c/b6d44072117bba057d50f7a2f96e5d070c65926dpatch
- https://git.kernel.org/stable/c/9ab896775f98ff54b68512f345eed178bf961084patch
- https://git.kernel.org/stable/c/1740a1e45eee65099a92fb502e1e67e63aad277dpatch
- https://git.kernel.org/stable/c/d0553680f94c49bbe0e39eb50d033ba563b4212dpatch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.