nfsd: fix deadlock secinfo+readdir compound

[ Upstream commit 2f6fc056e899bd0144a08da5cacaecbe8997cd74 ]

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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 864e2003e8ded5c8e6ff5db13f7fd9331ebefb65..2b50bc0c545e0d50e9e206cfe8f036f065fc6063 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -881,6 +881,7 @@ 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;