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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Chuck Lever <chuck.lever@oracle.com>,
        "J. Bruce Fields" <bfields@redhat.com>
Subject: [PATCH 4.19 160/191] NFSD: Add missing NFSv2 .pc_func methods
Date:   Tue,  3 Nov 2020 21:37:32 +0100
Message-Id: <20201103203247.490714915@linuxfoundation.org>
In-Reply-To: <20201103203232.656475008@linuxfoundation.org>
References: <20201103203232.656475008@linuxfoundation.org>
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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
@@ -615,6 +629,7 @@ 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),
@@ -652,6 +667,7 @@ 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),