scsi: megaraid_mm: Fix end of loop tests for list_for_each_entry()

The list_for_each_entry() iterator, "adapter" in this code, can never be
NULL.  If we exit the loop without finding the correct adapter then
"adapter" points invalid memory that is an offset from the list head.  This
will eventually lead to memory corruption and presumably a kernel crash.

Link: https://lore.kernel.org/r/20210708074642.23599-1-harshvardhan.jha@oracle.com
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Harshvardhan Jha <harshvardhan.jha@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/megaraid/megaraid_mm.c b/drivers/scsi/megaraid/megaraid_mm.c
index abf7b40..c509440 100644 (file)
--- a/drivers/scsi/megaraid/megaraid_mm.c
+++ b/drivers/scsi/megaraid/megaraid_mm.c
@@ -238,7 +238,7 @@ mraid_mm_get_adapter(mimd_t __user *umimd, int *rval)
        mimd_t          mimd;
        uint32_t        adapno;
        int             iterator;
-
+       bool            is_found;
 
        if (copy_from_user(&mimd, umimd, sizeof(mimd_t))) {
                *rval = -EFAULT;
@@ -254,12 +254,16 @@ mraid_mm_get_adapter(mimd_t __user *umimd, int *rval)
 
        adapter = NULL;
        iterator = 0;
+       is_found = false;
 
        list_for_each_entry(adapter, &adapters_list_g, list) {
-               if (iterator++ == adapno) break;
+               if (iterator++ == adapno) {
+                       is_found = true;
+                       break;
+               }
        }
 
-       if (!adapter) {
+       if (!is_found) {
                *rval = -ENODEV;
                return NULL;
        }
@@ -725,6 +729,7 @@ ioctl_done(uioc_t *kioc)
        uint32_t        adapno;
        int             iterator;
        mraid_mmadp_t*  adapter;
+       bool            is_found;
 
        /*
         * When the kioc returns from driver, make sure it still doesn't
@@ -747,19 +752,23 @@ ioctl_done(uioc_t *kioc)
                iterator        = 0;
                adapter         = NULL;
                adapno          = kioc->adapno;
+               is_found        = false;
 
                con_log(CL_ANN, ( KERN_WARNING "megaraid cmm: completed "
                                        "ioctl that was timedout before\n"));
 
                list_for_each_entry(adapter, &adapters_list_g, list) {
-                       if (iterator++ == adapno) break;
+                       if (iterator++ == adapno) {
+                               is_found = true;
+                               break;
+                       }
                }
 
                kioc->timedout = 0;
 
-               if (adapter) {
+               if (is_found)
                        mraid_mm_dealloc_kioc( adapter, kioc );
-               }
+
        }
        else {
                wake_up(&wait_q);