[lxc-devel] [PATCH] check for data in nla_put() to avoid invalid memcpy() calls

[Christian Brauner]

On Sun, Jul 29, 2018 at 05:44:06PM +0200, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal at milecki.pl>
> 
> It's a valid case to call nla_put() with NULL data and 0 len. It's done
> e.g. in the nla_put_attr().
> 
> There has to be a check for data in nla_put() as passing NULL to the
> memcpy() is not allowed. Even if length is 0, both pointers have to be
> valid.
> 
> For a reference see C99 standard (7.21.1/2), it says: "pointer arguments
> on such a call shall still have valid values".
> 
> Reported-by: Daniel Gimpelevich <daniel at gimpelevich.san-francisco.ca.us>
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>

Thanks, I've created a branch at https://github.com/lxc/lxc/pull/2497 .

Acked-by: Christian Brauner <christian.brauner at ubuntu.com>

> ---
>  src/lxc/nl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/lxc/nl.c b/src/lxc/nl.c
> index e1dd8443..dfe71110 100644
> --- a/src/lxc/nl.c
> +++ b/src/lxc/nl.c
> @@ -61,7 +61,8 @@ static int nla_put(struct nlmsg *nlmsg, int attr,
>  	rta = NLMSG_TAIL(nlmsg->nlmsghdr);
>  	rta->rta_type = attr;
>  	rta->rta_len = rtalen;
> -	memcpy(RTA_DATA(rta), data, len);
> +	if (data && len)
> +		memcpy(RTA_DATA(rta), data, len);
>  	nlmsg->nlmsghdr->nlmsg_len = tlen;
>  	return 0;
>  }
> -- 
> 2.13.7
> 
> _______________________________________________
> lxc-devel mailing list
> lxc-devel at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://lists.linuxcontainers.org/pipermail/lxc-devel/attachments/20180729/eaef0eed/attachment.sig>