linux-kernel - [PATCH] staging: vt6655: fix some erroneous memory clean-up loops

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Message-Id: <20220912170429.29852-1-namcaov@gmail.com>
Date:   Mon, 12 Sep 2022 19:04:31 +0200
From:   Nam Cao <namcaov@...il.com>
To:     forest@...ttletooquiet.net, gregkh@...uxfoundation.org
Cc:     namcaov@...il.com, ji_hun.kim@...sung.com,
        dan.carpenter@...cle.com, linux-kernel@...r.kernel.org,
        linux-staging@...ts.linux.dev
Subject: [PATCH] staging: vt6655: fix some erroneous memory clean-up loops

In some initialization functions of this driver, memory is allocated with
'i' acting as an index variable and increasing from 0. The commit in
"Fixes" introduces some clean-up codes in case of allocation failure,
which free memory in reverse order with 'i' decreasing to 0. However,
there are some problems:
  - The case i=0 is left out. Thus memory is leaked.
  - In case memory allocation fails right from the start, the memory
    freeing loops will start with i=-1 and invalid memory locations will
    be accessed.

One of these loops has been fixed in commit c8ff91535880 ("staging:
vt6655: fix potential memory leak"). Fix the remaining erroneous loops.

Link: https://lore.kernel.org/linux-staging/Yx9H1zSpxmNqx6Xc@kadam/
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: 5341ee0adb17 ("staging: vt6655: check for memory allocation failures")
Signed-off-by: Nam Cao <namcaov@...il.com>
---
 drivers/staging/vt6655/device_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/vt6655/device_main.c b/drivers/staging/vt6655/device_main.c
index 04d737012cef..56c3cf3ba53d 100644
--- a/drivers/staging/vt6655/device_main.c
+++ b/drivers/staging/vt6655/device_main.c
@@ -631,7 +631,7 @@ static int device_init_rd0_ring(struct vnt_private *priv)
 	kfree(desc->rd_info);
 
 err_free_desc:
-	while (--i) {
+	while (i--) {
 		desc = &priv->aRD0Ring[i];
 		device_free_rx_buf(priv, desc);
 		kfree(desc->rd_info);
@@ -677,7 +677,7 @@ static int device_init_rd1_ring(struct vnt_private *priv)
 	kfree(desc->rd_info);
 
 err_free_desc:
-	while (--i) {
+	while (i--) {
 		desc = &priv->aRD1Ring[i];
 		device_free_rx_buf(priv, desc);
 		kfree(desc->rd_info);
@@ -782,7 +782,7 @@ static int device_init_td1_ring(struct vnt_private *priv)
 	return 0;
 
 err_free_desc:
-	while (--i) {
+	while (i--) {
 		desc = &priv->apTD1Rings[i];
 		kfree(desc->td_info);
 	}
-- 
2.25.1