[PATCH v3 08/18] tftp: allocate buffers and fifo dynamically

[Enrico Scholz <enrico.scholz@sigma-chemnitz.de>]

Use the actual blocksize for allocating buffers instead of assuming an
hardcoded value.

This requires to add an additional 'START' state which is entered
after receiving (RRQ) or sending (WRQ) the OACK.  Without it, the next
state would be entered and the (not allocated yet) fifo be used.

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
---
 fs/tftp.c | 91 ++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 59 insertions(+), 32 deletions(-)

diff --git a/fs/tftp.c b/fs/tftp.c
index b552a5dc2f63..0b6d57c4603f 100644
--- a/fs/tftp.c
+++ b/fs/tftp.c
@@ -63,10 +63,12 @@
 #define STATE_WAITACK	6
 #define STATE_LAST	7
 #define STATE_DONE	8
+/* OACK from server has been received and we can begin to sent either the ACK
+   (for RRQ) or data (for WRQ) */
+#define STATE_START	9
 
 #define TFTP_BLOCK_SIZE		512	/* default TFTP block size */
 #define TFTP_MTU_SIZE		1432	/* MTU based block size */
-#define TFTP_FIFO_SIZE		4096
 
 #define TFTP_ERR_RESEND	1
 
@@ -106,6 +108,7 @@ static char const * const tftp_states[] = {
 	[STATE_WAITACK] = "WAITACK",
 	[STATE_LAST] = "LAST",
 	[STATE_DONE] = "DONE",
+	[STATE_START] = "START",
 };
 
 static int tftp_send(struct file_priv *priv)
@@ -294,19 +297,9 @@ static void tftp_recv(struct file_priv *priv,
 	case TFTP_OACK:
 		tftp_parse_oack(priv, pkt, len);
 		priv->tftp_con->udp->uh_dport = uh_sport;
-
-		if (priv->push) {
-			/* send first block */
-			priv->state = STATE_WDATA;
-			priv->block = 1;
-		} else {
-			/* send ACK */
-			priv->state = STATE_OACK;
-			priv->block = 0;
-			tftp_send(priv);
-		}
-
+		priv->state = STATE_START;
 		break;
+
 	case TFTP_DATA:
 		len -= 2;
 		priv->block = ntohs(*(uint16_t *)pkt);
@@ -330,6 +323,12 @@ static void tftp_recv(struct file_priv *priv,
 			/* Same block again; ignore it. */
 			break;
 
+		if (len > priv->blocksize) {
+			pr_warn("tftp: oversized packet (%u > %d) received\n",
+				len, priv->blocksize);
+			break;
+		}
+
 		priv->last_block = priv->block;
 
 		tftp_timer_reset(priv);
@@ -372,6 +371,36 @@ static void tftp_handler(void *ctx, char *packet, unsigned len)
 	tftp_recv(priv, pkt, net_eth_to_udplen(packet), udp->uh_sport);
 }
 
+
+static int tftp_start_transfer(struct file_priv *priv)
+{
+	priv->fifo = kfifo_alloc(priv->blocksize);
+	if (!priv->fifo)
+		return -ENOMEM;
+
+	if (priv->push) {
+		priv->buf = xmalloc(priv->blocksize);
+		if (!priv->buf) {
+			kfifo_free(priv->fifo);
+			priv->fifo = NULL;
+			return -ENOMEM;
+		}
+	}
+
+	if (priv->push) {
+		/* send first block */
+		priv->state = STATE_WDATA;
+		priv->block = 1;
+	} else {
+		/* send ACK */
+		priv->state = STATE_OACK;
+		priv->block = 0;
+		tftp_send(priv);
+	}
+
+	return 0;
+}
+
 static struct file_priv *tftp_do_open(struct device_d *dev,
 		int accmode, struct dentry *dentry)
 {
@@ -403,47 +432,45 @@ static struct file_priv *tftp_do_open(struct device_d *dev,
 	priv->blocksize = TFTP_BLOCK_SIZE;
 	priv->block_requested = -1;
 
-	priv->fifo = kfifo_alloc(TFTP_FIFO_SIZE);
-	if (!priv->fifo) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
 	parseopt_hu(fsdev->options, "port", &port);
 
 	priv->tftp_con = net_udp_new(tpriv->server, port, tftp_handler, priv);
 	if (IS_ERR(priv->tftp_con)) {
 		ret = PTR_ERR(priv->tftp_con);
-		goto out1;
+		goto out;
 	}
 
 	ret = tftp_send(priv);
 	if (ret)
-		goto out2;
+		goto out1;
 
 	tftp_timer_reset(priv);
-	while (priv->state != STATE_RDATA &&
-			priv->state != STATE_DONE &&
-			priv->state != STATE_WDATA) {
+	while (priv->state != STATE_DONE && priv->state != STATE_START) {
 		ret = tftp_poll(priv);
 		if (ret == TFTP_ERR_RESEND)
 			tftp_send(priv);
 		if (ret < 0)
-			goto out2;
+			goto out1;
 	}
 
-	if (priv->state == STATE_DONE && priv->err) {
+	if (priv->state == STATE_DONE) {
+		/* this should not happen; STATE_DONE without error happens
+		   after completing the transfer but this has not been started
+		   yet */
+		if (WARN_ON(priv->err == 0))
+			priv->err = -EIO;
+
 		ret = priv->err;
-		goto out2;
+		goto out1;
 	}
 
-	priv->buf = xmalloc(priv->blocksize);
+	ret = tftp_start_transfer(priv);
+	if (ret < 0)
+		goto out1;
 
 	return priv;
-out2:
-	net_unregister(priv->tftp_con);
 out1:
-	kfifo_free(priv->fifo);
+	net_unregister(priv->tftp_con);
 out:
 	free(priv);
 
@@ -561,7 +588,7 @@ static int tftp_read(struct device_d *dev, FILE *f, void *buf, size_t insize)
 		if (priv->state == STATE_DONE)
 			return outsize;
 
-		if (TFTP_FIFO_SIZE - kfifo_len(priv->fifo) >= priv->blocksize)
+		if (kfifo_len(priv->fifo) == 0)
 			tftp_send(priv);
 
 		ret = tftp_poll(priv);
-- 
2.37.1