[PATCH v2] scsi: do not leak information in ioctl

[Tom Rix <trix@xxxxxxxxxx>]

sr_ioctl.c uses this pattern

  result = sr_do_ioctl(cd, &cgc);
  to-user = buffer[];
  kfree(buffer);
  return result;

Use a buffer without checking leaks information.
Check result and jump over the use of buffer
if there is an error.

  result = sr_do_ioctl(cd, &cgc);
  if (result)
    goto err;
  to-user = buffer[];
err:
  kfree(buffer);
  return result;

Additionally initialize the buffer to zero.

This problem can be seen in the 2.4.0 kernel
However this scm only goes back as far as 2.6.12

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
---
v2 : split from combined pcd,scsi patch

 drivers/scsi/sr_ioctl.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/sr_ioctl.c b/drivers/scsi/sr_ioctl.c
index ddd00efc4882..fbdb5124d7f7 100644
--- a/drivers/scsi/sr_ioctl.c
+++ b/drivers/scsi/sr_ioctl.c
@@ -41,7 +41,7 @@ static int sr_read_tochdr(struct cdrom_device_info *cdi,
 	int result;
 	unsigned char *buffer;
 
-	buffer = kmalloc(32, GFP_KERNEL);
+	buffer = kzalloc(32, GFP_KERNEL);
 	if (!buffer)
 		return -ENOMEM;
 
@@ -55,10 +55,13 @@ static int sr_read_tochdr(struct cdrom_device_info *cdi,
 	cgc.data_direction = DMA_FROM_DEVICE;
 
 	result = sr_do_ioctl(cd, &cgc);
+	if (result)
+		goto err;
 
 	tochdr->cdth_trk0 = buffer[2];
 	tochdr->cdth_trk1 = buffer[3];
 
+err:
 	kfree(buffer);
 	return result;
 }
@@ -71,7 +74,7 @@ static int sr_read_tocentry(struct cdrom_device_info *cdi,
 	int result;
 	unsigned char *buffer;
 
-	buffer = kmalloc(32, GFP_KERNEL);
+	buffer = kzalloc(32, GFP_KERNEL);
 	if (!buffer)
 		return -ENOMEM;
 
@@ -86,6 +89,8 @@ static int sr_read_tocentry(struct cdrom_device_info *cdi,
 	cgc.data_direction = DMA_FROM_DEVICE;
 
 	result = sr_do_ioctl(cd, &cgc);
+	if (result)
+		goto err;
 
 	tocentry->cdte_ctrl = buffer[5] & 0xf;
 	tocentry->cdte_adr = buffer[5] >> 4;
@@ -98,6 +103,7 @@ static int sr_read_tocentry(struct cdrom_device_info *cdi,
 		tocentry->cdte_addr.lba = (((((buffer[8] << 8) + buffer[9]) << 8)
 			+ buffer[10]) << 8) + buffer[11];
 
+err:
 	kfree(buffer);
 	return result;
 }
@@ -384,7 +390,7 @@ int sr_get_mcn(struct cdrom_device_info *cdi, struct cdrom_mcn *mcn)
 {
 	Scsi_CD *cd = cdi->handle;
 	struct packet_command cgc;
-	char *buffer = kmalloc(32, GFP_KERNEL);
+	char *buffer = kzalloc(32, GFP_KERNEL);
 	int result;
 
 	if (!buffer)
@@ -400,10 +406,13 @@ int sr_get_mcn(struct cdrom_device_info *cdi, struct cdrom_mcn *mcn)
 	cgc.data_direction = DMA_FROM_DEVICE;
 	cgc.timeout = IOCTL_TIMEOUT;
 	result = sr_do_ioctl(cd, &cgc);
+	if (result)
+		goto err;
 
 	memcpy(mcn->medium_catalog_number, buffer + 9, 13);
 	mcn->medium_catalog_number[13] = 0;
 
+err:
 	kfree(buffer);
 	return result;
 }
-- 
2.27.0