Bug 2402721 (CVE-2025-39962)

Summary: CVE-2025-39962 kernel: rxrpc: Fix untrusted unsigned subtract
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-10-09 13:01:51 UTC 
In the Linux kernel, the following vulnerability has been resolved:

rxrpc: Fix untrusted unsigned subtract

Fix the following Smatch static checker warning:

   net/rxrpc/rxgk_app.c:65 rxgk_yfs_decode_ticket()
   warn: untrusted unsigned subtract. 'ticket_len - 10 * 4'

by prechecking the length of what we're trying to extract in two places in
the token and decoding for a response packet.

Also use sizeof() on the struct we're extracting rather specifying the size
numerically to be consistent with the other related statements.
Comment 1 Jon Moroney 2025-10-09 16:42:25 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100917-CVE-2025-39962-c0e0@gregkh/T