[74/90] [SCSI] sym53c8xx: Fix NULL pointer dereference in slave_destroy

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stratos Psomadakis <psomas@xxxxxxxxxx>

commit cced5041ed5a2d1352186510944b0ddfbdbe4c0b upstream.

sym53c8xx_slave_destroy unconditionally assumes that sym53c8xx_slave_alloc has
succesesfully allocated a sym_lcb. This can lead to a NULL pointer dereference
(exposed by commit 4e6c82b).

Signed-off-by: Stratos Psomadakis <psomas@xxxxxxxxxx>
Signed-off-by: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/scsi/sym53c8xx_2/sym_glue.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/scsi/sym53c8xx_2/sym_glue.c
+++ b/drivers/scsi/sym53c8xx_2/sym_glue.c
@@ -839,6 +839,10 @@ static void sym53c8xx_slave_destroy(stru
 	struct sym_lcb *lp = sym_lp(tp, sdev->lun);
 	unsigned long flags;
 
+	/* if slave_alloc returned before allocating a sym_lcb, return */
+	if (!lp)
+		return;
+
 	spin_lock_irqsave(np->s.host->host_lock, flags);
 
 	if (lp->busy_itlq || lp->busy_itl) {


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