Re: [PATCH net v2] net: wwan: t7xx: Fix off-by-one error in t7xx_dpmaif_rx_buf_alloc()

[Sergey Ryazanov]

On October 29, 2024 2:56:00 PM, Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
>The error path in t7xx_dpmaif_rx_buf_alloc(), free and unmap the already
>allocated and mapped skb in a loop, but the loop condition terminates when
>the index reaches zero, which fails to free the first allocated skb at
>index zero.
>
>Check for >= 0 so that skb at index 0 is freed as well.
>
>Fixes: d642b012df70 ("net: wwan: t7xx: Add data path interface")
>Suggested-by: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>
>Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

Jakub, when applying, could you drop that suggested-by tag, please. My contribution was only a small suggestion to avoid an endless loop. In all other meanings this patch is original work made by Jinjie, and all creds should go to him.

Besides that tag:

Acked-by: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>

>---
>v2:
>- Update the commit title.
>- Declare i as signed to avoid the endless loop.
>---
> drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c
>index 210d84c67ef9..45e7833965b1 100644
>--- a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c
>+++ b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c
>@@ -166,8 +166,8 @@ int t7xx_dpmaif_rx_buf_alloc(struct dpmaif_ctrl *dpmaif_ctrl,
> 			     const unsigned int q_num, const unsigned int buf_cnt,
> 			     const bool initial)
> {
>-	unsigned int i, bat_cnt, bat_max_cnt, bat_start_idx;
>-	int ret;
>+	unsigned int bat_cnt, bat_max_cnt, bat_start_idx;
>+	int ret, i;
> 
> 	if (!buf_cnt || buf_cnt > bat_req->bat_size_cnt)
> 		return -EINVAL;
>@@ -226,7 +226,7 @@ int t7xx_dpmaif_rx_buf_alloc(struct dpmaif_ctrl *dpmaif_ctrl,
> 	return 0;
> 
> err_unmap_skbs:
>-	while (--i > 0)
>+	while (--i >= 0)
> 		t7xx_unmap_bat_skb(dpmaif_ctrl->dev, bat_req->bat_skb, i);
> 
> 	return ret;