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

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

[Nam Cao]

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@oracle.com>
Fixes: 5341ee0adb17 ("staging: vt6655: check for memory allocation failures")
Signed-off-by: Nam Cao <namcaov@gmail.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

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

[Philipp Hortmann]

On 9/12/22 19:04, Nam Cao wrote:
> 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@oracle.com>
> Fixes: 5341ee0adb17 ("staging: vt6655: check for memory allocation failures")
> Signed-off-by: Nam Cao <namcaov@gmail.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);
>   	}

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>