CVE-2026-68416mtd: fix double free and WARN_ON in add_mtd_device() error paths

Official description

In the Linux kernel, the following vulnerability has been resolved: mtd: fix double free and WARN_ON in add_mtd_device() error paths When device_register() or mtd_nvmem_add() fails inside add_mtd_device() for a partition, the error handling triggers mtd_release() via put_device() or device_unregister(). mtd_release() calls release_mtd_partition() which frees the mtd_info structure. However, callers such as mtd_add_partition() and add_mtd_partitions() also call free_partition() in their error paths, resulting in a double free. Additionally, release_mtd_partition() hits WARN_ON(!list_empty( &mtd->part.node)) because the partition node is still linked in the parent's partitions list when the release callback fires from the add_mtd_device() error path. Fix this by overriding dev->type and dev->release before put_device() in the error paths, so that device_release() invokes a no-op function instead of mtd_release(). For the mtd_nvmem_add() failure case, device_unregister() is replaced with device_del() to separate the device removal from the final kobject reference drop, allowing the override to take effect before put_device() is called. The callers' error paths (list_del + free_partition) remain the sole owners of mtd_info lifetime on add_mtd_device() failure, which is the expected contract. The normal partition teardown path is not affected: del_mtd_device() goes through kref_put() -> mtd_device_release() -> device_unregister() with dev->type still set to &mtd_devtype, so mtd_release() -> release_mtd_partition() continues to work correctly for the regular removal case.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b1f78dc4a6869e30ff64345a5d3e7da1b6da0061
• https://git.kernel.org/stable/c/1dfe90daee6080b088b65620ff690a56f59ddea2
• https://git.kernel.org/stable/c/ffe21a3545b439e7b11578a701c22a847c149561
• https://git.kernel.org/stable/c/e1e96aca1bdf391e2f49531c270ffc134e5b49a5
• https://git.kernel.org/stable/c/f98ae09c727dcf34f745c875661c64b642e4abfa
• https://git.kernel.org/stable/c/820f983d641937a787e841ee4b93501f69f5683e
• https://git.kernel.org/stable/c/9d4af746af8ce27eefc2338b2feaa1e01f28b6c3