CVE-2026-80555: s390/vfio_ccw: Free all memory if cp_init() fails
In the Linux kernel, the following vulnerability has been resolved:
s390/vfioccw: Free all memory if cpinit() fails
The routine cpfree() is called to unpin/free any memory once an I/O is completed successfully, or if cpprefetch() fails. But if cpinit() fails, and cp->initialized is not enabled, the same routine cannot be used to free all the memory.
An attempt to address this exists in ccwchainhandleccw(), where a single call to ccwchainfree() is made for the currently-processed CCW segment. But this will leak other segments (created as a result of a Transfer in Channel) that had been allocated as part of the same channel program.
Address this by performing the cleanup outside of the recursive ccwchainhandleccw()/ccwchainlooptic() logic.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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On cp_init() failure, perform cleanup outside the recursive ccwchain_handle_ccw()/ccwchain_loop_tic() logic and call cp_free() even when cp->initialized is not enabled, so all memory—including segments allocated by Transfer in Channel—is unpinned and freed.
Event History
Frequently Asked Questions
Which systems are in scope?
The issue is in the Linux kernel's s390 vfio_ccw code path. It concerns channel programs that create additional CCW segments through Transfer in Channel processing.
What failure condition triggers the memory leak?
The leak occurs when cp_init() fails before cp->initialized is enabled. In that state, cp_free() cannot perform the normal full cleanup.
Why is freeing the currently processed CCW segment insufficient?
A single ccwchain_free() call for the current segment does not release other segments allocated for the same channel program. Those additional segments can have been created during recursive Transfer in Channel handling.