CVE-2026-89677

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

nfsd: fix possible fh compose of wrong dentry in nfsd4 create file()

dentry create() can hypothetically provide a different dentry than the one passed in. This could happen, for example, if the exported filesystem is NFS, and the server returned to OPEN a filehandle which matched a directory that was already in the dcache. Clearly this would not be expected!

If this were to happen the dentry (child) that was already stored in resfhp could be freed and later dereferenced.

We shouldn't call fh compose() until we are certain that we have the final dentry, so this patch moved the fh compose() call to two places: one for the case where the target already exists, and one after dentry create() where it was created.