[PATCH 2/6] sd: improve TUR handling in sd_check_events

Christoph Hellwig
2017-02-14T19:15:56Z

Remove bogus evaluations of retval and sshdr when the device is offline,
and fix a possible NULL pointer dereference by allocating the 8 byte
sized sense header on stack.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/scsi/sd.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 40b4038c019e..11e290d1dbff 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1425,7 +1425,6 @@ static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
{
struct scsi_disk *sdkp = scsi_disk_get(disk);
struct scsi_device *sdp;
- struct scsi_sense_hdr *sshdr = NULL;
int retval;

if (!sdkp)
@@ -1454,22 +1453,21 @@ static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
* by sd_spinup_disk() from sd_revalidate_disk(), which happens whenever
* sd_revalidate() is called.
*/
- retval = -ENODEV;
-
if (scsi_block_when_processing_errors(sdp)) {
- sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+ struct scsi_sense_hdr sshdr = { 0, };
+
retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES,
- sshdr);
- }
+ &sshdr);

- /* failed to execute TUR, assume media not present */
- if (host_byte(retval)) {
- set_media_not_present(sdkp);
- goto out;
- }
+ /* failed to execute TUR, assume media not present */
+ if (host_byte(retval)) {
+ set_media_not_present(sdkp);
+ goto out;
+ }

- if (media_not_present(sdkp, sshdr))
- goto out;
+ if (media_not_present(sdkp, &sshdr))
+ goto out;
+ }

/*
* For removable scsi disk we have to recognise the presence
@@ -1485,7 +1483,6 @@ static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
* Medium present state has changed in either direction.
* Device has indicated UNIT_ATTENTION.
*/
- kfree(sshdr);
retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
sdp->changed = 0;
scsi_disk_put(sdkp);
--
2.11.0