nfsd: fix deadlock secinfo+readdir compound

commit 2f6fc056e899bd0144a08da5cacaecbe8997cd74 upstream.

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.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 4cba7865f4966b825e3d47c7d423fdb8ca11a262..f8082c7cde8b1b9f4b430f7a7ca0b6abf2020c4d 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -878,6 +878,7 @@ 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;