Bug 2418871 (CVE-2025-40253)

Summary: CVE-2025-40253 kernel: s390/ctcm: Fix double-kfree
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Double-free corruption occurs in the s390 CTC MPC driver when mpc_rcvd_sweep_req() frees the mpcginfo structure, followed by ctcmpc_unpack_skb() freeing the same pointer. Clang's static analyzer flagged this ownership confusion. The duplicate kfree() corrupts slab metadata, potentially crashing the kernel or enabling exploitation.
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Description OSIDB Bzimport 2025-12-04 17:02:18 UTC 
In the Linux kernel, the following vulnerability has been resolved:

s390/ctcm: Fix double-kfree

The function 'mpc_rcvd_sweep_req(mpcginfo)' is called conditionally
from function 'ctcmpc_unpack_skb'. It frees passed mpcginfo.
After that a call to function 'kfree' in function 'ctcmpc_unpack_skb'
frees it again.

Remove 'kfree' call in function 'mpc_rcvd_sweep_req(mpcginfo)'.

Bug detected by the clang static analyzer.
Comment 1 Alexander B 2025-12-05 14:33:09 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120431-CVE-2025-40253-e855@gregkh/T