CVE-2021-47316

In the Linux kernel, the following vulnerability has been resolved: nfsd:
fix NULL dereference in nfs3svc_encode_getaclres In error cases the dentry
may be NULL. Before 20798dfe249a, the encoder also checked dentry and
d_really_is_positive(dentry), but that looks like overkill to me–zero
status should be enough to guarantee a positive dentry. This isn’t the
first time we’ve seen an error-case NULL dereference hidden in the
initialization of a local variable in an xdr encoder. But I went back
through the other recent rewrites and didn’t spot any similar bugs.