[PATCH AUTOSEL 4.4 4/6] scsi: megaraid_mm: Fix end of loop tests for list_for_each_entry()

[Sasha Levin]

From: Harshvardhan Jha <harshvardhan.jha@xxxxxxxxxx>

[ Upstream commit 77541f78eadfe9fdb018a7b8b69f0f2af2cf4b82 ]

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@xxxxxxxxxx
Acked-by: Sumit Saxena <sumit.saxena@xxxxxxxxxxxx>
Signed-off-by: Harshvardhan Jha <harshvardhan.jha@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/scsi/megaraid/megaraid_mm.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/megaraid/megaraid_mm.c b/drivers/scsi/megaraid/megaraid_mm.c
index a70692779a16..34067dfd2841 100644
--- a/drivers/scsi/megaraid/megaraid_mm.c
+++ b/drivers/scsi/megaraid/megaraid_mm.c
@@ -246,7 +246,7 @@ 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;
@@ -262,12 +262,16 @@ 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;
 	}
@@ -735,6 +739,7 @@ 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
@@ -757,19 +762,23 @@ 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);
-- 
2.30.2