NFS: Use xdr_stream-based XDR encoder for MNT's dirpath argument

Check the length of the supplied dirpath, and see that it fits
properly in the RPC buffer.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 44 insertions, 5 deletions

diff --git a/fs/nfs/mount_clnt.c b/fs/nfs/mount_clnt.c
index af45a374d56f..93361afcd5da 100644
--- a/fs/nfs/mount_clnt.c
+++ b/fs/nfs/mount_clnt.c
@@ -21,6 +21,21 @@
 #endif
 
 /*
+ * Defined by RFC 1094, section A.3; and RFC 1813, section 5.1.4
+ */
+#define MNTPATHLEN              (1024)
+
+/*
+ * XDR data type sizes
+ */
+#define encode_dirpath_sz       (1 + XDR_QUADLEN(MNTPATHLEN))
+
+/*
+ * XDR argument and result sizes
+ */
+#define MNT_enc_dirpath_sz      encode_dirpath_sz
+
+/*
  * Defined by RFC 1094, section A.5
  */
 enum {
@@ -135,6 +150,31 @@ static int xdr_encode_dirpath(struct rpc_rqst *req, __be32 *p,
         return 0;
 }
 
+static int encode_mntdirpath(struct xdr_stream *xdr, const char *pathname)
+{
+        const u32 pathname_len = strlen(pathname);
+        __be32 *p;
+
+        if (unlikely(pathname_len > MNTPATHLEN))
+                return -EIO;
+
+        p = xdr_reserve_space(xdr, sizeof(u32) + pathname_len);
+        if (unlikely(p == NULL))
+                return -EIO;
+        xdr_encode_opaque(p, pathname, pathname_len);
+
+        return 0;
+}
+
+static int mnt_enc_dirpath(struct rpc_rqst *req, __be32 *p,
+                           const char *dirpath)
+{
+        struct xdr_stream xdr;
+
+        xdr_init_encode(&xdr, &req->rq_snd_buf, p);
+        return encode_mntdirpath(&xdr, dirpath);
+}
+
 static int xdr_decode_fhstatus(struct rpc_rqst *req, __be32 *p,
                                struct mnt_fhstatus *res)
 {
@@ -164,16 +204,15 @@ static int xdr_decode_fhstatus3(struct rpc_rqst *req, __be32 *p,
         return 0;
 }
 
-#define MNT_dirpath_sz          (1 + 256)
 #define MNT_fhstatus_sz         (1 + 8)
 #define MNT_fhstatus3_sz        (1 + 16)
 
 static struct rpc_procinfo mnt_procedures[] = {
         [MOUNTPROC_MNT] = {
                 .p_proc         = MOUNTPROC_MNT,
-                .p_encode       = (kxdrproc_t) xdr_encode_dirpath,
+                .p_encode       = (kxdrproc_t)mnt_enc_dirpath,
                 .p_decode       = (kxdrproc_t) xdr_decode_fhstatus,
-                .p_arglen       = MNT_dirpath_sz,
+                .p_arglen       = MNT_enc_dirpath_sz,
                 .p_replen       = MNT_fhstatus_sz,
                 .p_statidx      = MOUNTPROC_MNT,
                 .p_name         = "MOUNT",
@@ -183,9 +222,9 @@ static struct rpc_procinfo mnt_procedures[] = {
 static struct rpc_procinfo mnt3_procedures[] = {
         [MOUNTPROC3_MNT] = {
                 .p_proc         = MOUNTPROC3_MNT,
-                .p_encode       = (kxdrproc_t) xdr_encode_dirpath,
+                .p_encode       = (kxdrproc_t)mnt_enc_dirpath,
                 .p_decode       = (kxdrproc_t) xdr_decode_fhstatus3,
-                .p_arglen       = MNT_dirpath_sz,
+                .p_arglen       = MNT_enc_dirpath_sz,
                 .p_replen       = MNT_fhstatus3_sz,
                 .p_statidx      = MOUNTPROC3_MNT,
                 .p_name         = "MOUNT",