If previous write command is still pending then free it first.

As per the current kernel driver design, write operation prepares a
buffer for FSI write, the actual FSI write is performed on next read
operation. There is a possibility of memory leak if buggy application
sends two back to back writes or two parallel writes.

Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
---
v3:
  - Incorporated review comments by Eddie.
---
 drivers/fsi/fsi-sbefifo.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index a95b32461f8f3..1cc88a78e588a 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -877,6 +877,13 @@ static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
 
 	mutex_lock(&user->file_lock);
 
+	/* If previous write command is still pending then free it. It is safe
+	 * to do that because read cannot be in progress since we hold the
+	 * lock.
+	 */
+	if (user->pending_cmd)
+		sbefifo_release_command(user);
+
 	/* Can we use the pre-allocate buffer ? If not, allocate */
 	if (len <= PAGE_SIZE)
 		user->pending_cmd = user->cmd_page;
-- 
2.39.2

On 10/10/23 15:43, Ninad Palsule wrote:
> If previous write command is still pending then free it first.
>
> As per the current kernel driver design, write operation prepares a
> buffer for FSI write, the actual FSI write is performed on next read
> operation. There is a possibility of memory leak if buggy application
> sends two back to back writes or two parallel writes.


Reviewed-by: Eddie James <eajames@linux.ibm.com>


>
> Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
> ---
> v3:
>    - Incorporated review comments by Eddie.
> ---
>   drivers/fsi/fsi-sbefifo.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
> index a95b32461f8f3..1cc88a78e588a 100644
> --- a/drivers/fsi/fsi-sbefifo.c
> +++ b/drivers/fsi/fsi-sbefifo.c
> @@ -877,6 +877,13 @@ static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
>   
>   	mutex_lock(&user->file_lock);
>   
> +	/* If previous write command is still pending then free it. It is safe
> +	 * to do that because read cannot be in progress since we hold the
> +	 * lock.
> +	 */
> +	if (user->pending_cmd)
> +		sbefifo_release_command(user);
> +
>   	/* Can we use the pre-allocate buffer ? If not, allocate */
>   	if (len <= PAGE_SIZE)
>   		user->pending_cmd = user->cmd_page;