nfsd: fix deadlock secinfo+readdir compound

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.

Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 410516e9867f06a30d2690774acf72eee6e88329..40b912407d5149288de1fd01e02c925be11acd76 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -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;