netdev - Re: [PATCH] iphase: Adding a null pointer check

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Message-ID: <d8884b3c-bef4-7042-934b-0bcdb4347b97@ispras.ru>
Date: Mon, 8 Jan 2024 20:28:31 +0300
From: Alexey Khoroshilov <khoroshilov@...ras.ru>
To: Andrey Shumilin <shum.sdl@...ct.ru>, 3chas3@...il.com
Cc: linux-atm-general@...ts.sourceforge.net, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] iphase: Adding a null pointer check

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@...ct.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