Messages in this thread | | | From | Aleksandr Mikhalitsyn <> | Date | Mon, 13 Mar 2023 12:40:28 +0100 | Subject | Re: [PATCH net-next v2] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC |
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+CC security subsystem folks
On Mon, Mar 13, 2023 at 12:32 PM Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com> wrote: > > Currently, kernel would set MSG_CTRUNC flag if msg_control buffer > wasn't provided and SO_PASSCRED was set or if there was pending SCM_RIGHTS. > > For some reason we have no corresponding check for SO_PASSSEC. > > In the recvmsg(2) doc we have: > MSG_CTRUNC > indicates that some control data was discarded due to lack > of space in the buffer for ancillary data. > > So, we need to set MSG_CTRUNC flag for all types of SCM. > > This change can break applications those don't check MSG_CTRUNC flag. > > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: Leon Romanovsky <leon@kernel.org> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com> > > v2: > - commit message was rewritten according to Eric's suggestion > --- > include/net/scm.h | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/include/net/scm.h b/include/net/scm.h > index 1ce365f4c256..585adc1346bd 100644 > --- a/include/net/scm.h > +++ b/include/net/scm.h > @@ -105,16 +105,27 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc > } > } > } > + > +static inline bool scm_has_secdata(struct socket *sock) > +{ > + return test_bit(SOCK_PASSSEC, &sock->flags); > +} > #else > static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm) > { } > + > +static inline bool scm_has_secdata(struct socket *sock) > +{ > + return false; > +} > #endif /* CONFIG_SECURITY_NETWORK */ > > static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, > struct scm_cookie *scm, int flags) > { > if (!msg->msg_control) { > - if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp) > + if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp || > + scm_has_secdata(sock)) > msg->msg_flags |= MSG_CTRUNC; > scm_destroy(scm); > return; > -- > 2.34.1 >
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