netdev - Re: [PATCH net] gtp: allow -1 to be specified as file description from userspace

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Message-ID: <93352553-9015-46fa-8797-52cb94ce14df@sysmocom.de>
Date: Wed, 23 Oct 2024 11:26:58 +0200
From: Oliver Smith <osmith@...mocom.de>
To: Pablo Neira Ayuso <pablo@...filter.org>, netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
 edumazet@...gle.com, fw@...len.de, pespin@...mocom.de, laforge@...monks.org,
 osmocom-net-gprs@...ts.osmocom.org
Subject: Re: [PATCH net] gtp: allow -1 to be specified as file description
 from userspace

Hello Pablo,

I've reproduced the regression:

> 20241023090545167 DGGSN NOTICE Initialized GTP kernel mode (genl ID is 32) (gtp-kernel.c:80)
> [    0.721705] gtp: enable gtp on -1, 4
> [    0.722017] gtp: gtp socket fd=-1 not found
> 20241023090545169 DTUN ERROR cannot create GTP tunnel device: Bad file descriptor (tun.c:213)

and verified that it is fixed with your patch. Thanks!

Best regards,
Oliver

On 22.10.24 16:48, Pablo Neira Ayuso wrote:
> Existing user space applications maintained by the Osmocom project are
> breaking since a recent fix that addresses incorrect error checking.
> 
> Restore operation for user space programs that specify -1 as file
> descriptor to skip GTPv0 or GTPv1 only sockets.
> 
> Fixes: defd8b3c37b0 ("gtp: fix a potential NULL pointer dereference")
> Reported-by: Pau Espin Pedrol <pespin@...mocom.de>

Tested-by: Oliver Smith <osmith@...mocom.de>

> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> ---
>   drivers/net/gtp.c | 22 +++++++++++++---------
>   1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
> index a60bfb1abb7f..70f981887518 100644
> --- a/drivers/net/gtp.c
> +++ b/drivers/net/gtp.c
> @@ -1702,20 +1702,24 @@ static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[])
>   		return -EINVAL;
>   
>   	if (data[IFLA_GTP_FD0]) {
> -		u32 fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
> +		int fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
>   
> -		sk0 = gtp_encap_enable_socket(fd0, UDP_ENCAP_GTP0, gtp);
> -		if (IS_ERR(sk0))
> -			return PTR_ERR(sk0);
> +		if (fd0 >= 0) {
> +			sk0 = gtp_encap_enable_socket(fd0, UDP_ENCAP_GTP0, gtp);
> +			if (IS_ERR(sk0))
> +				return PTR_ERR(sk0);
> +		}
>   	}
>   
>   	if (data[IFLA_GTP_FD1]) {
> -		u32 fd1 = nla_get_u32(data[IFLA_GTP_FD1]);
> +		int fd1 = nla_get_u32(data[IFLA_GTP_FD1]);
>   
> -		sk1u = gtp_encap_enable_socket(fd1, UDP_ENCAP_GTP1U, gtp);
> -		if (IS_ERR(sk1u)) {
> -			gtp_encap_disable_sock(sk0);
> -			return PTR_ERR(sk1u);
> +		if (fd1 >= 0) {
> +			sk1u = gtp_encap_enable_socket(fd1, UDP_ENCAP_GTP1U, gtp);
> +			if (IS_ERR(sk1u)) {
> +				gtp_encap_disable_sock(sk0);
> +				return PTR_ERR(sk1u);
> +			}
>   		}
>   	}
>   

-- 
- Oliver Smith <osmith@...mocom.de>            https://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Siemensstr. 26a
* 10551 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Director: Harald Welte