[PATCH 4.7 100/141] cxl: fix potential NULL dereference in free_adapter()

[Greg Kroah-Hartman]

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

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

From: Andrew Donnellan <andrew.donnel...@au1.ibm.com>

commit 8fbaa51d43ef2c6a72849ec34060910723a0365f upstream.

If kzalloc() fails when allocating adapter->guest in
cxl_guest_init_adapter(), we call free_adapter() before erroring out.
free_adapter() in turn attempts to dereference adapter->guest, which in
this case is NULL.

In free_adapter(), skip the adapter->guest cleanup if adapter->guest is
NULL.

Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
Reported-by: Dan Carpenter <dan.carpen...@oracle.com>
Signed-off-by: Andrew Donnellan <andrew.donnel...@au1.ibm.com>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/misc/cxl/guest.c |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

--- a/drivers/misc/cxl/guest.c
+++ b/drivers/misc/cxl/guest.c
@@ -1052,16 +1052,18 @@ static void free_adapter(struct cxl *ada
        struct irq_avail *cur;
        int i;
 
-       if (adapter->guest->irq_avail) {
-               for (i = 0; i < adapter->guest->irq_nranges; i++) {
-                       cur = &adapter->guest->irq_avail[i];
-                       kfree(cur->bitmap);
+       if (adapter->guest) {
+               if (adapter->guest->irq_avail) {
+                       for (i = 0; i < adapter->guest->irq_nranges; i++) {
+                               cur = &adapter->guest->irq_avail[i];
+                               kfree(cur->bitmap);
+                       }
+                       kfree(adapter->guest->irq_avail);
                }
-               kfree(adapter->guest->irq_avail);
+               kfree(adapter->guest->status);
+               kfree(adapter->guest);
        }
-       kfree(adapter->guest->status);
        cxl_remove_adapter_nr(adapter);
-       kfree(adapter->guest);
        kfree(adapter);
 }