2023-10-13 07:06:09

by Ma Ke

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

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 protected]>
---
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;

msg.skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
if (!msg.skb)
--
2.37.2

2023-10-13 08:57:36

by Vadim Fedorenko

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

On 13/10/2023 08:04, Ma Ke 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 protected]>
> ---
> 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;

The better choice would be to use strncmp() with limit of
TIPC_MAX_LINK_NAME in tipc_node_find_by_name().
This patch fixes tipc_nl_node_get_link(), but the same pattern is used
in tipc_nl_node_set_link() and tipc_nl_node_reset_link_stats(), these
functions also need improvements. Changes to strncmp() and strnstr()
will fix all spots.

>
> msg.skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
> if (!msg.skb)

2023-10-13 09:21:28

by Florian Westphal

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

Ma Ke <[email protected]> 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 protected]>
> ---
> 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.

2023-10-14 00:17:32

by Jakub Kicinski

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

On Fri, 13 Oct 2023 15:04:08 +0800 Ma Ke 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 protected]>

You have now sent 14 incorrect fixes to Linux networking.
And not a single correct one.
I would like to politely ask you to stop.