Bug 2393163 (CVE-2025-38682)

Summary: CVE-2025-38682 kernel: i2c: core: Fix double-free of fwnode in i2c_unregister_device()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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OS: Linux   
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Description OSIDB Bzimport 2025-09-04 16:01:58 UTC
In the Linux kernel, the following vulnerability has been resolved:

i2c: core: Fix double-free of fwnode in i2c_unregister_device()

Before commit df6d7277e552 ("i2c: core: Do not dereference fwnode in struct
device"), i2c_unregister_device() only called fwnode_handle_put() on
of_node-s in the form of calling of_node_put(client->dev.of_node).

But after this commit the i2c_client's fwnode now unconditionally gets
fwnode_handle_put() on it.

When the i2c_client has no primary (ACPI / OF) fwnode but it does have
a software fwnode, the software-node will be the primary node and
fwnode_handle_put() will put() it.

But for the software fwnode device_remove_software_node() will also put()
it leading to a double free:

[   82.665598] ------------[ cut here ]------------
[   82.665609] refcount_t: underflow; use-after-free.
[   82.665808] WARNING: CPU: 3 PID: 1502 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x11
...
[   82.666830] RIP: 0010:refcount_warn_saturate+0xba/0x110
...
[   82.666962]  <TASK>
[   82.666971]  i2c_unregister_device+0x60/0x90

Fix this by not calling fwnode_handle_put() when the primary fwnode is
a software-node.