CVE-2026-93106crash_dump: release keyring reference at the correct time

Official description

In the Linux kernel, the following vulnerability has been resolved: crash_dump: release keyring reference at the correct time restore_dm_crypt_keys_to_thread_keyring() gets a reference to the user keyring before restoring the saved dm-crypt keys. The same keyring reference is then passed to add_key_to_keyring() for each saved key, but add_key_to_keyring() drops that reference on every call. This is only balanced when exactly one key is restored. With multiple keys, the keyring reference is dropped too many times and may trigger a refcount underflow or use-after-free. When more than five keys are restored, a refcount underflow/use-after-free warning can be triggered. The early error paths after lookup_user_key() also return without dropping the keyring reference. Keep ownership of the keyring reference in restore_dm_crypt_keys_to_thread_keyring(), drop it once on all exit paths, and make add_key_to_keyring() only use the reference without consuming it.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b0f7343a002f9c8b8378011f60482c76f3216dfd
• https://git.kernel.org/stable/c/ed566979f99c5516cad45a76ae25e2a4928ffb67
• https://git.kernel.org/stable/c/ada2e5a44e99113e08ad9b7b71396c6c572204da