nfsd: fix deadlock secinfo+readdir compound

From: "J. Bruce Fields" <[email protected]>

nfsd_lookup_dentry exits with the parent filehandle locked. fh_put also unlocks if necessary (nfsd filehandle locking is probably too lenient), so it gets unlocked eventually, but if the following op in the compound needs to lock it again, we can deadlock.

A fuzzer ran into this; normal clients don't send a secinfo followed by a readdir in the same compound.

---
 fs/nfsd/nfs4proc.c | 1 +
 1 file changed, 1 insertion(+)

index 410516e9867f..40b912407d51 100644
@@ -876,6 +876,7 @@ nfsd4_secinfo(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 				    &exp, &dentry);
 	if (err)
 		return err;
+	fh_unlock(&cstate->current_fh);
 	if (d_really_is_negative(dentry)) {
 		exp_put(exp);
 		err = nfserr_noent;

2.5.0