| Message ID | 20210920154232.15494-1-tim.gardner@canonical.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [next] mptcp: Avoid NULL dereference in mptcp_getsockopt_subflow_addrs() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | warning | Target tree name not specified in the subject |
| netdev/cc_maintainers | success | CCed 6 of 6 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 1 this patch: 1 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 9 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 1 this patch: 1 |
| netdev/header_inline | success | Link |
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 <mathew.j.martineau@linux.intel.com> > Cc: Matthieu Baerts <matthieu.baerts@tessares.net> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: netdev@vger.kernel.org > Cc: mptcp@lists.linux.dev > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Tim Gardner <tim.gardner@canonical.com> > > [ 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 <mathew.j.martineau@linux.intel.com> >> Cc: Matthieu Baerts <matthieu.baerts@tessares.net> >> Cc: "David S. Miller" <davem@davemloft.net> >> Cc: Jakub Kicinski <kuba@kernel.org> >> Cc: netdev@vger.kernel.org >> Cc: mptcp@lists.linux.dev >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Tim Gardner <tim.gardner@canonical.com> >> >> [ 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
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;
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 <mathew.j.martineau@linux.intel.com> Cc: Matthieu Baerts <matthieu.baerts@tessares.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jakub Kicinski <kuba@kernel.org> Cc: netdev@vger.kernel.org Cc: mptcp@lists.linux.dev Cc: linux-kernel@vger.kernel.org Signed-off-by: Tim Gardner <tim.gardner@canonical.com> [ 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(+)