The pointer <dev->desc_tbl[i].iavcc> is dereferenced on line 195.
Further in the code, it is checked for null on line 204.
It is proposed to add a check before dereferencing the pointer.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Andrey Shumilin <shum.sdl@nppct.ru>
---
 drivers/atm/iphase.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/atm/iphase.c b/drivers/atm/iphase.c
index 324148686953..596422fbfacc 100644
--- a/drivers/atm/iphase.c
+++ b/drivers/atm/iphase.c
@@ -192,6 +192,11 @@ static u16 get_desc (IADEV *dev, struct ia_vcc *iavcc) {
            i++;
            continue;
         }
+       if (!(iavcc_r = dev->desc_tbl[i].iavcc)) {
+	   printk("Fatal err, desc table vcc or skb is NULL\n");
+	   i++;
+	   continue;
+	}
         ltimeout = dev->desc_tbl[i].iavcc->ltimeout; 
         delta = jiffies - dev->desc_tbl[i].timestamp;
         if (delta >= ltimeout) {
-- 
2.30.2

Proposal for subject:

atm: iphase: Move check for NULL before derefence in get_desc()


On 07.11.2023 15:36, Andrey Shumilin wrote:
> The pointer <dev->desc_tbl[i].iavcc> is dereferenced on line 195.
> Further in the code, it is checked for null on line 204.
> It is proposed to add a check before dereferencing the pointer.

Line numbers in commit messages are not welcome since they are subject
for change and a reader of the message likely has other code at that
lines in his version of the file.

> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Andrey Shumilin <shum.sdl@nppct.ru>
> ---
>  drivers/atm/iphase.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/atm/iphase.c b/drivers/atm/iphase.c
> index 324148686953..596422fbfacc 100644
> --- a/drivers/atm/iphase.c
> +++ b/drivers/atm/iphase.c
> @@ -192,6 +192,11 @@ static u16 get_desc (IADEV *dev, struct ia_vcc *iavcc) {
>             i++;
>             continue;
>          }
> +       if (!(iavcc_r = dev->desc_tbl[i].iavcc)) {
> +	   printk("Fatal err, desc table vcc or skb is NULL\n");
> +	   i++;
> +	   continue;
> +	}

Error message should be fixed, skb is not check for NULL here.

>          ltimeout = dev->desc_tbl[i].iavcc->ltimeout; 
>          delta = jiffies - dev->desc_tbl[i].timestamp;
>          if (delta >= ltimeout) {
> 


>           if (!dev->desc_tbl[i].txskb || !(iavcc_r =
dev->desc_tbl[i].iavcc))
>              printk("Fatal err, desc table vcc or skb is NULL\n");


The existing check should be fixed to check for skb only.

--
Alexey

On Tue,  7 Nov 2023 15:36:00 +0300 Andrey Shumilin wrote:
> The pointer <dev->desc_tbl[i].iavcc> is dereferenced on line 195.
> Further in the code, it is checked for null on line 204.
> It is proposed to add a check before dereferencing the pointer.

How do you know this is the right way to address the problem.
Much easier to debug a crash than misbehaving driver.

This is ancient code, leave it be.
-- 
pw-bot: reject
pv-bot: nit