Coverity complains of a possible NULL dereference in
mptcp_getsockopt_subflow_addrs():
861 } else if (sk->sk_family == AF_INET6) {
3. returned_null: inet6_sk returns NULL. [show details]
4. var_assigned: Assigning: np = NULL return value from inet6_sk.
862 const struct ipv6_pinfo *np = inet6_sk(sk);
Fix this by checking for NULL.
Cc: Mat Martineau <[email protected]>
Cc: Matthieu Baerts <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Tim Gardner <[email protected]>
[ I'm not at all sure this is the right thing to do since the final result is to
return garbage to user space in mptcp_getsockopt_subflow_addrs(). Is this one
of those cases where inet6_sk() can't fail ?]
---
net/mptcp/sockopt.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 8137cc3a4296..c89f2bedce79 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -861,6 +861,9 @@ static void mptcp_get_sub_addrs(const struct sock *sk, struct mptcp_subflow_addr
} else if (sk->sk_family == AF_INET6) {
const struct ipv6_pinfo *np = inet6_sk(sk);
+ if (!np)
+ return;
+
a->sin6_local.sin6_family = AF_INET6;
a->sin6_local.sin6_port = inet->inet_sport;
--
2.33.0
On Mon, 20 Sep 2021, Tim Gardner wrote:
> Coverity complains of a possible NULL dereference in
> mptcp_getsockopt_subflow_addrs():
>
> 861 } else if (sk->sk_family == AF_INET6) {
> 3. returned_null: inet6_sk returns NULL. [show details]
> 4. var_assigned: Assigning: np = NULL return value from inet6_sk.
> 862 const struct ipv6_pinfo *np = inet6_sk(sk);
>
> Fix this by checking for NULL.
>
> Cc: Mat Martineau <[email protected]>
> Cc: Matthieu Baerts <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Jakub Kicinski <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Tim Gardner <[email protected]>
>
> [ I'm not at all sure this is the right thing to do since the final result is to
> return garbage to user space in mptcp_getsockopt_subflow_addrs(). Is this one
> of those cases where inet6_sk() can't fail ?]
Hi Tim -
Thanks for noticing this and proposing a fix.
As you commented, this isn't the right change to merge since
mptcp_getsockopt_subflow_addrs() would copy garbage.
This block of code already checks that CONFIG_IPV6 is enabled, so the
question is whether sk_fullsock() would return false because the subflow
is in TCP_TIME_WAIT or TCP_NEW_SYN_RECV. The caller is iterating over
sockets in the MPTCP socket's conn_list, which does not contain
request_socks (so there are no sockets in the TCP_NEW_SYN_RECV state).
TCP subflow sockets are normally removed from the conn_list before they
are closed by their parent MPTCP socket, but I need to double-check for
corner cases. I created a github issue to track this:
https://github.com/multipath-tcp/mptcp_net-next/issues/231
Thanks,
Mat
> ---
> net/mptcp/sockopt.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
> index 8137cc3a4296..c89f2bedce79 100644
> --- a/net/mptcp/sockopt.c
> +++ b/net/mptcp/sockopt.c
> @@ -861,6 +861,9 @@ static void mptcp_get_sub_addrs(const struct sock *sk, struct mptcp_subflow_addr
> } else if (sk->sk_family == AF_INET6) {
> const struct ipv6_pinfo *np = inet6_sk(sk);
>
> + if (!np)
> + return;
> +
> a->sin6_local.sin6_family = AF_INET6;
> a->sin6_local.sin6_port = inet->inet_sport;
>
> --
> 2.33.0
>
>
--
Mat Martineau
Intel
On Mon, 20 Sep 2021, Mat Martineau wrote:
> On Mon, 20 Sep 2021, Tim Gardner wrote:
>
>> Coverity complains of a possible NULL dereference in
>> mptcp_getsockopt_subflow_addrs():
>>
>> 861 } else if (sk->sk_family == AF_INET6) {
>> 3. returned_null: inet6_sk returns NULL. [show details]
>> 4. var_assigned: Assigning: np = NULL return value from inet6_sk.
>> 862 const struct ipv6_pinfo *np = inet6_sk(sk);
>>
>> Fix this by checking for NULL.
>>
>> Cc: Mat Martineau <[email protected]>
>> Cc: Matthieu Baerts <[email protected]>
>> Cc: "David S. Miller" <[email protected]>
>> Cc: Jakub Kicinski <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>> Signed-off-by: Tim Gardner <[email protected]>
>>
>> [ I'm not at all sure this is the right thing to do since the final result is to
>> return garbage to user space in mptcp_getsockopt_subflow_addrs(). Is this one
>> of those cases where inet6_sk() can't fail ?]
>
> Hi Tim -
>
> Thanks for noticing this and proposing a fix.
>
> As you commented, this isn't the right change to merge since
> mptcp_getsockopt_subflow_addrs() would copy garbage.
>
> This block of code already checks that CONFIG_IPV6 is enabled, so the
> question is whether sk_fullsock() would return false because the subflow is
> in TCP_TIME_WAIT or TCP_NEW_SYN_RECV. The caller is iterating over sockets in
> the MPTCP socket's conn_list, which does not contain request_socks (so there
> are no sockets in the TCP_NEW_SYN_RECV state).
>
> TCP subflow sockets are normally removed from the conn_list before they are
> closed by their parent MPTCP socket, but I need to double-check for corner
> cases. I created a github issue to track this:
> https://github.com/multipath-tcp/mptcp_net-next/issues/231
>
Tim,
Could you submit a v2 of this patch? Paolo took a look and the condition
should not happen, but adding the NULL check would be a good idea and
returning early as your patch does is ok. The data copied after the early
return will be zeroed and look like the address family is AF_UNSPEC.
Could you add a
Fixes: https://github.com/multipath-tcp/mptcp_net-next/issues/231
tag and make the one change below?
>
>> ---
>> net/mptcp/sockopt.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
>> index 8137cc3a4296..c89f2bedce79 100644
>> --- a/net/mptcp/sockopt.c
>> +++ b/net/mptcp/sockopt.c
>> @@ -861,6 +861,9 @@ static void mptcp_get_sub_addrs(const struct sock *sk,
>> struct mptcp_subflow_addr
>> } else if (sk->sk_family == AF_INET6) {
>> const struct ipv6_pinfo *np = inet6_sk(sk);
>>
>> + if (!np)
This could be
if (WARN_ON_ONCE(!np))
(as suggested by Paolo) to make it clear the condition is unexpected.
>> + return;
>> +
>> a->sin6_local.sin6_family = AF_INET6;
>> a->sin6_local.sin6_port = inet->inet_sport;
>>
>> --
>> 2.33.0
Thanks,
--
Mat Martineau
Intel