Re: [RFC] sandbox: prevent segfault in tap_alloc()

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Antony,

On Wed, Jun 19, 2019 at 01:49:16PM +0300, Antony Pavlov wrote:
> Tap network interface initialization in sandbox
> barebox leads to segfault under Debian Buster/Sid.
> 
> The problem is that strcpy(dev, ifr.ifr_name) inside
> tap_alloc() tries to alter read-only data passed
> by tap_probe() and barebox receives SIGSEGV.
> 
> Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
> ---
>  drivers/net/tap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> index 1fbfa085b1..d7e32f4875 100644
> --- a/drivers/net/tap.c
> +++ b/drivers/net/tap.c
> @@ -14,7 +14,7 @@
>  
>  struct tap_priv {
>  	int fd;
> -	char *name;
> +	char name[128];
>  };
>  
>  static int tap_eth_send(struct eth_device *edev, void *packet, int length)
> @@ -65,7 +65,7 @@ static int tap_probe(struct device_d *dev)
>  	int ret = 0;
>  
>  	priv = xzalloc(sizeof(struct tap_priv));
> -	priv->name = "barebox";
> +	strncpy(priv->name, "barebox", sizeof(priv->name));
>  
>  	priv->fd = tap_alloc(priv->name);

Can we change the prototype of tap_alloc() to something like this:

int tap_alloc(const char *name, int *fd, char **outname);

outname would be an allocated string to be freed by the caller.

Sascha

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