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SubjectRe: [PATCH] net: qrtr: fix memory leak in qrtr_tun_read_iter
On Wed, Sep 25, 2019 at 06:04:13PM -0500, Navid Emamdoost wrote:
> In qrtr_tun_read_iter we need an error handling path to appropriately
> release skb in cases of error.

Release _what_ skb?

> Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> ---
> net/qrtr/tun.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> index e35869e81766..0f6e6d1d2901 100644
> --- a/net/qrtr/tun.c
> +++ b/net/qrtr/tun.c
> @@ -54,19 +54,24 @@ static ssize_t qrtr_tun_read_iter(struct kiocb *iocb, struct iov_iter *to)
> int count;
>
> while (!(skb = skb_dequeue(&tun->queue))) {

The body of the loop is entered only if the loop condition has
evaluated true. In this case, it means that the value of
!(skb = skb_dequeue(&tun->queue))
had been true, i.e. the value of
skb = skb_dequeue(&tun->queue)
has been NULL, i.e. that skb_dequeue() has returned NULL, which had
been copied into skb.

In other words, in the body of that loop we have skb equal to NULL.

> - if (filp->f_flags & O_NONBLOCK)
> - return -EAGAIN;
> + if (filp->f_flags & O_NONBLOCK) {
> + count = -EAGAIN;
> + goto out;
> + }
>
> /* Wait until we get data or the endpoint goes away */
> if (wait_event_interruptible(tun->readq,
> - !skb_queue_empty(&tun->queue)))
> - return -ERESTARTSYS;
> + !skb_queue_empty(&tun->queue))) {
> + count = -ERESTARTSYS;
> + goto out;
> + }
> }

The meaning of that loop is fairly clear, isn't it? Keep looking int
tun->queue until an skb shows up there. If it's not immediately there,
fail with -EAGAIN for non-blocking files and wait on tun->readq until
some skb arrives.

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