Merge tag 'staging-6.18-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

Pull staging driver fixes from Greg KH:
 "Here are some staging driver fixes that missed 6.17-final due to my
  travel schedule. They fix a number of reported issues in the axis-fifo
  driver, one of which was just independently discovered by someone else
  today so someone is looking at this code.

  All of these fixes have been in linux-next for many weeks with no
  reported issues"

* tag 'staging-6.18-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: axis-fifo: flush RX FIFO on read errors
  staging: axis-fifo: fix TX handling on copy_from_user() failure
  staging: axis-fifo: fix maximum TX packet length check

Author: torvalds

drivers/staging/axis-fifo/axis-fifo.c

@@ -43,7 +43,6 @@
 #define DRIVER_NAME "axis_fifo"
 
 #define READ_BUF_SIZE 128U /* read buffer length in words */
-#define WRITE_BUF_SIZE 128U /* write buffer length in words */
 
 #define AXIS_FIFO_DEBUG_REG_NAME_MAX_LEN	4
 
@@ -231,6 +230,7 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 	}
 
 	bytes_available = ioread32(fifo->base_addr + XLLF_RLR_OFFSET);
+	words_available = bytes_available / sizeof(u32);
 	if (!bytes_available) {
 		dev_err(fifo->dt_device, "received a packet of length 0\n");
 		ret = -EIO;
@@ -241,7 +241,7 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 		dev_err(fifo->dt_device, "user read buffer too small (available bytes=%zu user buffer bytes=%zu)\n",
 			bytes_available, len);
 		ret = -EINVAL;
-		goto end_unlock;
+		goto err_flush_rx;
 	}
 
 	if (bytes_available % sizeof(u32)) {
@@ -250,11 +250,9 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 		 */
 		dev_err(fifo->dt_device, "received a packet that isn't word-aligned\n");
 		ret = -EIO;
-		goto end_unlock;
+		goto err_flush_rx;
 	}
 
-	words_available = bytes_available / sizeof(u32);
-
 	/* read data into an intermediate buffer, copying the contents
 	 * to userspace when the buffer is full
 	 */
@@ -266,18 +264,23 @@ static ssize_t axis_fifo_read(struct file *f, char __user *buf,
 			tmp_buf[i] = ioread32(fifo->base_addr +
 					      XLLF_RDFD_OFFSET);
 		}
+		words_available -= copy;
 
 		if (copy_to_user(buf + copied * sizeof(u32), tmp_buf,
 				 copy * sizeof(u32))) {
 			ret = -EFAULT;
-			goto end_unlock;
+			goto err_flush_rx;
 		}
 
 		copied += copy;
-		words_available -= copy;
 	}
+	mutex_unlock(&fifo->read_lock);
+
+	return bytes_available;
 
-	ret = bytes_available;
+err_flush_rx:
+	while (words_available--)
+		ioread32(fifo->base_addr + XLLF_RDFD_OFFSET);
 
 end_unlock:
 	mutex_unlock(&fifo->read_lock);
@@ -305,11 +308,8 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 {
 	struct axis_fifo *fifo = (struct axis_fifo *)f->private_data;
 	unsigned int words_to_write;
-	unsigned int copied;
-	unsigned int copy;
-	unsigned int i;
+	u32 *txbuf;
 	int ret;
-	u32 tmp_buf[WRITE_BUF_SIZE];
 
 	if (len % sizeof(u32)) {
 		dev_err(fifo->dt_device,
@@ -325,11 +325,17 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 		return -EINVAL;
 	}
 
-	if (words_to_write > fifo->tx_fifo_depth) {
-		dev_err(fifo->dt_device, "tried to write more words [%u] than slots in the fifo buffer [%u]\n",
-			words_to_write, fifo->tx_fifo_depth);
+	/*
+	 * In 'Store-and-Forward' mode, the maximum packet that can be
+	 * transmitted is limited by the size of the FIFO, which is
+	 * (C_TX_FIFO_DEPTH–4)*(data interface width/8) bytes.
+	 *
+	 * Do not attempt to send a packet larger than 'tx_fifo_depth - 4',
+	 * otherwise a 'Transmit Packet Overrun Error' interrupt will be
+	 * raised, which requires a reset of the TX circuit to recover.
+	 */
+	if (words_to_write > (fifo->tx_fifo_depth - 4))
 		return -EINVAL;
-	}
 
 	if (fifo->write_flags & O_NONBLOCK) {
 		/*
@@ -368,32 +374,20 @@ static ssize_t axis_fifo_write(struct file *f, const char __user *buf,
 		}
 	}
 
-	/* write data from an intermediate buffer into the fifo IP, refilling
-	 * the buffer with userspace data as needed
-	 */
-	copied = 0;
-	while (words_to_write > 0) {
-		copy = min(words_to_write, WRITE_BUF_SIZE);
-
-		if (copy_from_user(tmp_buf, buf + copied * sizeof(u32),
-				   copy * sizeof(u32))) {
-			ret = -EFAULT;
-			goto end_unlock;
-		}
-
-		for (i = 0; i < copy; i++)
-			iowrite32(tmp_buf[i], fifo->base_addr +
-				  XLLF_TDFD_OFFSET);
-
-		copied += copy;
-		words_to_write -= copy;
+	txbuf = vmemdup_user(buf, len);
+	if (IS_ERR(txbuf)) {
+		ret = PTR_ERR(txbuf);
+		goto end_unlock;
 	}
 
-	ret = copied * sizeof(u32);
+	for (int i = 0; i < words_to_write; ++i)
+		iowrite32(txbuf[i], fifo->base_addr + XLLF_TDFD_OFFSET);
 
 	/* write packet size to fifo */
-	iowrite32(ret, fifo->base_addr + XLLF_TLR_OFFSET);
+	iowrite32(len, fifo->base_addr + XLLF_TLR_OFFSET);
 
+	ret = len;
+	kvfree(txbuf);
 end_unlock:
 	mutex_unlock(&fifo->write_lock);