[PATCH 4.14 096/125] NFSD: Add missing NFSv2 .pc_func methods

Greg Kroah-Hartman
2020-11-03T21:12:35Z

From: Chuck Lever <chuck.lever@oracle.com>

commit 6b3dccd48de8a4c650b01499a0b09d1e2279649e upstream.

There's no protection in nfsd_dispatch() against a NULL .pc_func
helpers. A malicious NFS client can trigger a crash by invoking the
unused/unsupported NFSv2 ROOT or WRITECACHE procedures.

The current NFSD dispatcher does not support returning a void reply
to a non-NULL procedure, so the reply to both of these is wrong, for
the moment.

Cc: <stable@vger.kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfsd/nfsproc.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -118,6 +118,13 @@ done:
return nfsd_return_attrs(nfserr, resp);
}

+/* Obsolete, replaced by MNTPROC_MNT. */
+static __be32
+nfsd_proc_root(struct svc_rqst *rqstp)
+{
+ return nfs_ok;
+}
+
/*
* Look up a path name component
* Note: the dentry in the resp->fh may be negative if the file
@@ -201,6 +208,13 @@ nfsd_proc_read(struct svc_rqst *rqstp)
return fh_getattr(&resp->fh, &resp->stat);
}

+/* Reserved */
+static __be32
+nfsd_proc_writecache(struct svc_rqst *rqstp)
+{
+ return nfs_ok;
+}
+
/*
* Write data to a file
* N.B. After this call resp->fh needs an fh_put
@@ -605,6 +619,7 @@ static const struct svc_procedure nfsd_p
.pc_xdrressize = ST+AT,
},
[NFSPROC_ROOT] = {
+ .pc_func = nfsd_proc_root,
.pc_decode = nfssvc_decode_void,
.pc_encode = nfssvc_encode_void,
.pc_argsize = sizeof(struct nfsd_void),
@@ -642,6 +657,7 @@ static const struct svc_procedure nfsd_p
.pc_xdrressize = ST+AT+1+NFSSVC_MAXBLKSIZE_V2/4,
},
[NFSPROC_WRITECACHE] = {
+ .pc_func = nfsd_proc_writecache,
.pc_decode = nfssvc_decode_void,
.pc_encode = nfssvc_encode_void,
.pc_argsize = sizeof(struct nfsd_void),