Subject: Re: [PATCH] tipc: Fix uninit-value access in tipc_nl_node_get_link()

From: Florian Westphal <[email-masked]>
Date: Fri, 13 Oct 2023 11:20:04 +0200

Ma Ke <[email-masked]> wrote:
> Names must be null-terminated strings. If a name which is not 
> null-terminated is passed through netlink, strstr() and similar 
> functions can cause buffer overrun. This patch fixes this issue 
> by returning -EINVAL if a non-null-terminated name is passed.
> 
> Signed-off-by: Ma Ke <[email-masked]>
> ---
>  net/tipc/node.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/tipc/node.c b/net/tipc/node.c
> index 3105abe97bb9..a02bcd7e07d3 100644
> --- a/net/tipc/node.c
> +++ b/net/tipc/node.c
> @@ -2519,6 +2519,9 @@ int tipc_nl_node_get_link(struct sk_buff *skb, struct genl_info *info)
>  		return -EINVAL;
>  
>  	name = nla_data(attrs[TIPC_NLA_LINK_NAME]);
> +	if (name[strnlen(name,
> +			 nla_len(attrs[TIPC_NLA_LINK_NAME]))] != '\0')
> +		return -EINVAL;

If the existing userspace is passing 0-terminated strings it would be
better to fix the policy (tipc_nl_link_policy) instead (and set NLA_NUL_STRING).

And if not, above change breaks userspace.