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@gmail.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
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;
-- 
2.34.1

On October 29, 2024 2:56:00 PM, Jinjie Ruan <ruanjinjie@huawei.com> 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@gmail.com>
>Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>

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@gmail.com>

>---
>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;

On Wed, 30 Oct 2024 18:01:07 +0200 Sergey Ryazanov wrote:
> On October 29, 2024 2:56:00 PM, Jinjie Ruan <ruanjinjie@huawei.com> 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@gmail.com>
> >Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>  
> 
> 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.

TBH I find the while (i--) solution suggested by Ilpo more idiomatic,
too, let's do a v3 with that and without unnecessary Suggested-by tags.