On 15/08/2019 09:30, Dan Carpenter wrote:
> We recently added a kfree() after the end of the loop:
>
> if (retries == RETRIES) {
> kfree(reply);
> return -EINVAL;
> }
>
> There are two problems. First the test is wrong and because retries
> equals RETRIES if we succeed on the last iteration through the loop.
> Second if we fail on the last iteration through the loop then the kfree
> is a double free.
>
> When you're reading this code, please note the break statement at the
> end of the while loop. This patch changes the loop so that if it's not
> successful then "reply" is NULL and we can test for that afterward.
>
> Fixes: 6b7c3b86f0b6 ("drm/vmwgfx: fix memory leak when too many retries have occurred")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> drivers/gpu/drm/vmwgfx/vmwgfx_msg.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> index 59e9d05ab928..0af048d1a815 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
> @@ -353,7 +353,7 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
> !!(HIGH_WORD(ecx) & MESSAGE_STATUS_HB));
> if ((HIGH_WORD(ebx) & MESSAGE_STATUS_SUCCESS) == 0) {
> kfree(reply);
> -
> + reply = NULL;
> if ((HIGH_WORD(ebx) & MESSAGE_STATUS_CPT) != 0) {
> /* A checkpoint occurred. Retry. */
> continue;
> @@ -377,7 +377,7 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
>
> if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0) {
> kfree(reply);
> -
> + reply = NULL;
> if ((HIGH_WORD(ecx) & MESSAGE_STATUS_CPT) != 0) {
> /* A checkpoint occurred. Retry. */
> continue;
> @@ -389,10 +389,8 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
> break;
> }
>
> - if (retries == RETRIES) {
> - kfree(reply);
> + if (!reply)
> return -EINVAL;
> - }
>
> *msg_len = reply_len;
> *msg = reply;
>
Dan, Thanks for fixing up my mistake.
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