CVE-2021-4454

Summary

CVE-2021-4454 is a vulnerability affecting the Linux kernel's j1939 subsystem. Contrary to initial assumptions, j1939_session_deactivate() can be called with a session ref-count less than 2. However, this does not pose a problem as the function checks the session's active state before deactivation. A concurrent scenario involving j1939_session_get_by_addr and j1939_session_deactivate was reported by syzbot, resulting in a WARN_ON_ONCE error. Despite the warning, the system remained stable, demonstrating that the vulnerability does not lead to a critical issue.

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