CVE-2026-72316

In the Linux kernel, the following vulnerability has been resolved:

dm era: fix NULL pointer dereference in metadata_open()

metadata_open() returns NULL when kzalloc_obj() fails, but the
caller era_ctr() only checks IS_ERR(md).  Since IS_ERR(NULL)
returns false, the NULL pointer is treated as a valid result
and later assigned to era->md, leading to a NULL pointer
dereference when the metadata is accessed.

Fix this by returning ERR_PTR(-ENOMEM) on allocation failure,
consistent with dm-cache-metadata.c, dm-thin-metadata.c, and
dm-clone-metadata.c which all use ERR_PTR(-ENOMEM) for the
same pattern.