Bug 2406196 (CVE-2025-40018)

Summary: CVE-2025-40018 kernel: ipvs: Defer ip_vs_ftp unregister during netns cleanup
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-10-24 12:01:26 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ipvs: Defer ip_vs_ftp unregister during netns cleanup

On the netns cleanup path, __ip_vs_ftp_exit() may unregister ip_vs_ftp
before connections with valid cp->app pointers are flushed, leading to a
use-after-free.

Fix this by introducing a global `exiting_module` flag, set to true in
ip_vs_ftp_exit() before unregistering the pernet subsystem. In
__ip_vs_ftp_exit(), skip ip_vs_ftp unregister if called during netns
cleanup (when exiting_module is false) and defer it to
__ip_vs_cleanup_batch(), which unregisters all apps after all connections
are flushed. If called during module exit, unregister ip_vs_ftp
immediately.
Comment 1 Keith Grant 2025-10-24 13:32:18 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025102433-CVE-2025-40018-96db@gregkh/T