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 6ed585935d5e854d66612631583a14b7b21a57a6..606d5aa33d7688fd09ab021647866c2fed7b0b00 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 (dentry->d_inode == NULL) {
                exp_put(exp);
                err = nfserr_noent;