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

[Simon Horman <horms@kernel.org>]

+ Cong and Andrew

On Tue, Oct 22, 2024 at 04:48:25PM +0200, 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@sysmocom.de>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Reviewed-by: Simon Horman <horms@kernel.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);
> +			}
>  		}
>  	}
>  
> -- 
> 2.30.2
> 
>