CVE-2026-64059

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

netfs: Fix folio->private handling in netfsperformwrite()

Under some circumstances, netfsperformwrite() doesn't correctly manipulate folio->private between NULL, NETFSFOLIOCOPYTOCACHE, pointing to a group and pointing to a netfsfolio struct, leading to potential multiple attachments of private data with associated folio ref leaks and also leaks of netfsfolio structs or netfs_group refs.

Fix this by consolidating the place at which a folio is marked uptodate in one place and having that look at what's attached to folio->private and decide how to clean it up and then set the new group. Also, the content shouldn't be flushed if group is NULL, even if a group is specified in the netfsgroup parameter, as that would be the case for a new folio. A filesystem should always specify netfsgroup or never specify netfs_group.

The Sashiko auto-review tool noted that it was theoretically possible that the fpos >= ctx->zero_point section might leak if it modified a streaming write folio. This is unlikely, but with a network filesystem, third party changes can happen. It also pointed out that __netfssetgroup() would leak if called multiple times on the same folio from the "whole folio modify section".