* Re: [PATCH net-next v2] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC
[not found] ` <CAEivzxf630y_kjVLNM4m1vfQxnwyOBK+0wiCLW1T+8miPVC5Fg@mail.gmail.com>
@ 2023-03-13 20:43 ` Paul Moore
2023-03-14 11:06 ` Aleksandr Mikhalitsyn
0 siblings, 1 reply; 2+ messages in thread
From: Paul Moore @ 2023-03-13 20:43 UTC (permalink / raw)
To: Aleksandr Mikhalitsyn
Cc: davem, linux-kernel, netdev, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Leon Romanovsky, jmorris, serge,
linux-security-module, selinux
On Mon, Mar 13, 2023 at 7:40 AM Aleksandr Mikhalitsyn
<aleksandr.mikhalitsyn@canonical.com> wrote:
>
> +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.
Unless I'm missing something I don't think this will actually result
in a userspace visible change as put_cmsg() already has a number of
checks which set the MSG_CTRUNC flag if necessary (including if no
control buffer is passed, e.g. msg_control == NULL).
Regardless, it looks fine to me.
Acked-by: Paul Moore <paul@paul-moore.com>
> > 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
--
paul-moore.com
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH net-next v2] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC
2023-03-13 20:43 ` [PATCH net-next v2] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC Paul Moore
@ 2023-03-14 11:06 ` Aleksandr Mikhalitsyn
0 siblings, 0 replies; 2+ messages in thread
From: Aleksandr Mikhalitsyn @ 2023-03-14 11:06 UTC (permalink / raw)
To: Paul Moore
Cc: davem, linux-kernel, netdev, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, Leon Romanovsky, jmorris, serge,
linux-security-module, selinux
On Mon, Mar 13, 2023 at 9:43 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Mon, Mar 13, 2023 at 7:40 AM Aleksandr Mikhalitsyn
> <aleksandr.mikhalitsyn@canonical.com> wrote:
> >
> > +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.
>
> Unless I'm missing something I don't think this will actually result
> in a userspace visible change as put_cmsg() already has a number of
> checks which set the MSG_CTRUNC flag if necessary (including if no
> control buffer is passed, e.g. msg_control == NULL).
Yes you are right. I found this check suspicious while working on
SCM_PIDFD (which is not yet submitted to LKML),
I think it is worth fixing that check anyway just for consistency reasons.
>
> Regardless, it looks fine to me.
>
> Acked-by: Paul Moore <paul@paul-moore.com>
Thanks, Paul!
Regards,
Alex
>
> > > 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
>
> --
> paul-moore.com
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2023-03-13 20:43 ` [PATCH net-next v2] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC Paul Moore
2023-03-14 11:06 ` Aleksandr Mikhalitsyn
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