[PATCH] nfs: check return value of various rpc calls

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

Check more carefully for failing requests. This improves the error
message when trying to mount a non-exported nfs directory from:

	nfs_mount_req: file handle too big: 44831

to

	nfs_mount_req: Mounting gave error NFS3ERR_ACCES(0xd)

.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
 fs/nfs.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 81 insertions(+), 10 deletions(-)

diff --git a/fs/nfs.c b/fs/nfs.c
index 15ddab7915df..0be32322fb65 100644
--- a/fs/nfs.c
+++ b/fs/nfs.c
@@ -636,13 +636,33 @@ static uint32_t *nfs_read_post_op_attr(uint32_t *p, struct inode *inode)
 	return p;
 }
 
+static int nfserror_to_err(u32 nfserror, const char **errorname)
+{
+#define E(NFSERR, ERR)			\
+	case NFSERR:			\
+		*errorname = #NFSERR;	\
+		return -ERR
+
+	switch (nfserror) {
+	E(NFS3_OK, 0);
+	E(NFS3ERR_NOENT, ENOENT);
+	E(NFS3ERR_IO, EIO);
+	E(NFS3ERR_ACCES, EACCES);
+	E(NFS3ERR_NOTDIR, ENOTDIR);
+	E(NFS3ERR_NAMETOOLONG, ENAMETOOLONG);
+
+	default:
+		*errorname = "???";
+		return -EINVAL;
+	}
+}
 /*
  * nfs_mount_req - Mount an NFS Filesystem
  */
 static int nfs_mount_req(struct nfs_priv *npriv)
 {
 	uint32_t data[1024];
-	uint32_t *p;
+	uint32_t *p, status;
 	int len;
 	int pathlen;
 	struct packet *nfs_packet;
@@ -667,7 +687,21 @@ static int nfs_mount_req(struct nfs_priv *npriv)
 	if (IS_ERR(nfs_packet))
 		return PTR_ERR(nfs_packet);
 
-	p = (void *)nfs_packet->data + sizeof(struct rpc_reply) + 4;
+	p = (void *)nfs_packet->data + sizeof(struct rpc_reply);
+
+	/*
+	 * Theoretically the error status is one of MNT3ERR_..., but the NFS
+	 * constants are identical.
+	 */
+	status = ntoh32(net_read_uint32(p++));
+	if (status != NFS3_OK) {
+		const char *error;
+		int ret;
+
+		ret = nfserror_to_err(status, &error);
+		printf("%s: Mounting gave error %s(0x%x)\n", __func__, error, status);
+		return -ret;
+	}
 
 	npriv->rootfh.size = ntoh32(net_read_uint32(p++));
 	if (npriv->rootfh.size > NFS3_FHSIZE) {
@@ -719,7 +753,7 @@ static int nfs_lookup_req(struct nfs_priv *npriv, struct nfs_fh *fh,
 {
 	struct nfs_inode *ninode = nfsi(inode);
 	uint32_t data[1024];
-	uint32_t *p;
+	uint32_t *p, status;
 	int len;
 	struct packet *nfs_packet;
 
@@ -761,7 +795,16 @@ static int nfs_lookup_req(struct nfs_priv *npriv, struct nfs_fh *fh,
 	if (IS_ERR(nfs_packet))
 		return PTR_ERR(nfs_packet);
 
-	p = (void *)nfs_packet->data + sizeof(struct rpc_reply) + 4;
+	p = (void *)nfs_packet->data + sizeof(struct rpc_reply);
+	status = ntoh32(net_read_uint32(p++));
+	if (status != NFS3_OK) {
+		const char *error;
+		int ret;
+
+		ret = nfserror_to_err(status, &error);
+		printf("%s: LOOKUP failed with error %s(0x%x)\n", __func__, error, status);
+		return ret;
+	}
 
 	ninode->fh.size = ntoh32(net_read_uint32(p++));
 	if (ninode->fh.size > NFS3_FHSIZE) {
@@ -787,7 +830,7 @@ static int nfs_lookup_req(struct nfs_priv *npriv, struct nfs_fh *fh,
 static void *nfs_readdirattr_req(struct nfs_priv *npriv, struct nfs_dir *dir)
 {
 	uint32_t data[1024];
-	uint32_t *p;
+	uint32_t *p, status;
 	int len;
 	struct packet *nfs_packet;
 	void *buf;
@@ -845,7 +888,17 @@ static void *nfs_readdirattr_req(struct nfs_priv *npriv, struct nfs_dir *dir)
 	if (IS_ERR(nfs_packet))
 		return NULL;
 
-	p = (void *)nfs_packet->data + sizeof(struct rpc_reply) + 4;
+	p = (void *)nfs_packet->data + sizeof(struct rpc_reply);
+	status = ntoh32(net_read_uint32(p++));
+	if (status != NFS3_OK) {
+		const char *error;
+		int ret;
+
+		ret = nfserror_to_err(status, &error);
+		printf("%s: READDIR failed with error %s(%u)\n", __func__, error, status);
+		return NULL;
+	}
+
 	p = nfs_read_post_op_attr(p, NULL);
 
 	/* update cookieverf */
@@ -879,7 +932,7 @@ static int nfs_read_req(struct file_priv *priv, uint64_t offset,
 		uint32_t readlen)
 {
 	uint32_t data[1024];
-	uint32_t *p;
+	uint32_t *p, status;
 	int len;
 	struct packet *nfs_packet;
 	uint32_t rlen, eof;
@@ -922,7 +975,16 @@ static int nfs_read_req(struct file_priv *priv, uint64_t offset,
 	if (IS_ERR(nfs_packet))
 		return PTR_ERR(nfs_packet);
 
-	p = (void *)nfs_packet->data + sizeof(struct rpc_reply) + 4;
+	p = (void *)nfs_packet->data + sizeof(struct rpc_reply);
+	status = ntoh32(net_read_uint32(p++));
+	if (status != NFS3_OK) {
+		const char *error;
+		int ret;
+
+		ret = nfserror_to_err(status, &error);
+		printf("%s: READ failed with error %s(0x%x)\n", __func__, error, status);
+		return ret;
+	}
 
 	p = nfs_read_post_op_attr(p, NULL);
 
@@ -981,7 +1043,7 @@ static int nfs_readlink_req(struct nfs_priv *npriv, struct nfs_fh *fh,
 			    char **target)
 {
 	uint32_t data[1024];
-	uint32_t *p;
+	uint32_t *p, status;
 	uint32_t len;
 	struct packet *nfs_packet;
 
@@ -1017,7 +1079,16 @@ static int nfs_readlink_req(struct nfs_priv *npriv, struct nfs_fh *fh,
 	if (IS_ERR(nfs_packet))
 		return PTR_ERR(nfs_packet);
 
-	p = (void *)nfs_packet->data + sizeof(struct rpc_reply) + 4;
+	p = (void *)nfs_packet->data + sizeof(struct rpc_reply);
+	status = ntoh32(net_read_uint32(p++));
+	if (status != NFS3_OK) {
+		const char *error;
+		int ret;
+
+		ret = nfserror_to_err(status, &error);
+		printf("%s: READLINK failed with error %s(0x%x)\n", __func__, error, status);
+		return ret;
+	}
 
 	p = nfs_read_post_op_attr(p, NULL);
 
-- 
2.28.0


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