ALSA: vx: Fix possible transfer overflow

The pseudo DMA transfer codes in VX222 and VX-pocket driver have a
slight bug where they check the buffer boundary wrongly, and may
overflow.  Also, the zero sample count might be handled badly for the
playback (although it shouldn't happen in theory).  This patch
addresses these issues.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=141541
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/vx/vx_pcm.c

@@ -1048,8 +1048,10 @@ static void vx_pcm_capture_update(struct vx_core *chip, struct snd_pcm_substream
 		/* ok, let's accelerate! */
 		int align = pipe->align * 3;
 		space = (count / align) * align;
-		vx_pseudo_dma_read(chip, runtime, pipe, space);
-		count -= space;
+		if (space > 0) {
+			vx_pseudo_dma_read(chip, runtime, pipe, space);
+			count -= space;
+		}
 	}
 	/* read the rest of bytes */
 	while (count > 0) {

sound/pci/vx222/vx222_ops.c

@@ -269,12 +269,12 @@ static void vx2_dma_write(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 
 	/* Transfer using pseudo-dma.
 	 */
-	if (offset + count > pipe->buffer_bytes) {
+	if (offset + count >= pipe->buffer_bytes) {
 		int length = pipe->buffer_bytes - offset;
 		count -= length;
 		length >>= 2; /* in 32bit words */
 		/* Transfer using pseudo-dma. */
-		while (length-- > 0) {
+		for (; length > 0; length--) {
 			outl(cpu_to_le32(*addr), port);
 			addr++;
 		}
@@ -284,7 +284,7 @@ static void vx2_dma_write(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 	pipe->hw_ptr += count;
 	count >>= 2; /* in 32bit words */
 	/* Transfer using pseudo-dma. */
-	while (count-- > 0) {
+	for (; count > 0; count--) {
 		outl(cpu_to_le32(*addr), port);
 		addr++;
 	}
@@ -307,20 +307,20 @@ static void vx2_dma_read(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 	vx2_setup_pseudo_dma(chip, 0);
 	/* Transfer using pseudo-dma.
 	 */
-	if (offset + count > pipe->buffer_bytes) {
+	if (offset + count >= pipe->buffer_bytes) {
 		int length = pipe->buffer_bytes - offset;
 		count -= length;
 		length >>= 2; /* in 32bit words */
 		/* Transfer using pseudo-dma. */
-		while (length-- > 0)
+		for (; length > 0; length--)
 			*addr++ = le32_to_cpu(inl(port));
 		addr = (u32 *)runtime->dma_area;
 		pipe->hw_ptr = 0;
 	}
 	pipe->hw_ptr += count;
 	count >>= 2; /* in 32bit words */
 	/* Transfer using pseudo-dma. */
-	while (count-- > 0)
+	for (; count > 0; count--)
 		*addr++ = le32_to_cpu(inl(port));
 
 	vx2_release_pseudo_dma(chip);

sound/pcmcia/vx/vxp_ops.c

@@ -369,12 +369,12 @@ static void vxp_dma_write(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 	unsigned short *addr = (unsigned short *)(runtime->dma_area + offset);
 
 	vx_setup_pseudo_dma(chip, 1);
-	if (offset + count > pipe->buffer_bytes) {
+	if (offset + count >= pipe->buffer_bytes) {
 		int length = pipe->buffer_bytes - offset;
 		count -= length;
 		length >>= 1; /* in 16bit words */
 		/* Transfer using pseudo-dma. */
-		while (length-- > 0) {
+		for (; length > 0; length--) {
 			outw(cpu_to_le16(*addr), port);
 			addr++;
 		}
@@ -384,7 +384,7 @@ static void vxp_dma_write(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 	pipe->hw_ptr += count;
 	count >>= 1; /* in 16bit words */
 	/* Transfer using pseudo-dma. */
-	while (count-- > 0) {
+	for (; count > 0; count--) {
 		outw(cpu_to_le16(*addr), port);
 		addr++;
 	}
@@ -411,20 +411,20 @@ static void vxp_dma_read(struct vx_core *chip, struct snd_pcm_runtime *runtime,
 	if (snd_BUG_ON(count % 2))
 		return;
 	vx_setup_pseudo_dma(chip, 0);
-	if (offset + count > pipe->buffer_bytes) {
+	if (offset + count >= pipe->buffer_bytes) {
 		int length = pipe->buffer_bytes - offset;
 		count -= length;
 		length >>= 1; /* in 16bit words */
 		/* Transfer using pseudo-dma. */
-		while (length-- > 0)
+		for (; length > 0; length--)
 			*addr++ = le16_to_cpu(inw(port));
 		addr = (unsigned short *)runtime->dma_area;
 		pipe->hw_ptr = 0;
 	}
 	pipe->hw_ptr += count;
 	count >>= 1; /* in 16bit words */
 	/* Transfer using pseudo-dma. */
-	while (count-- > 1)
+	for (; count > 1; count--)
 		*addr++ = le16_to_cpu(inw(port));
 	/* Disable DMA */
 	pchip->regDIALOG &= ~VXP_DLG_DMAREAD_SEL_MASK;