Subject: Re: [PATCH net] sctp: fix copying more bytes than expected in sctp_add_bind_addr

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Mon, 7 Mar 2016 16:51:15 -0300

On Mon, Mar 07, 2016 at 08:45:20PM +0100, Dmitry Vyukov wrote:
> Yes, it is. I never saw this bug again. Forgot to update this thread. Sorry.

Cool, thanks. The patch isn't applied yet, so either some other patch
fixed it and this patch not necessary anymore or you kept the patch
applied.  Please confirm which one :-)

> On Mon, Mar 7, 2016 at 8:44 PM, Marcelo Ricardo Leitner
> <[email-masked]> wrote:
> > On Tue, Jan 26, 2016 at 02:28:48PM +0100, Dmitry Vyukov wrote:
> >> On Mon, Jan 25, 2016 at 6:52 PM, Marcelo Ricardo Leitner
> >> <[email-masked]> wrote:
> >> > Great. Dmitry, please give this a run. Local tests looked good but who
> >> > knows what syzkaller may find.
> >>
> >> Now running with this patch.
> >
> > Hi Dmitry, do you remember if this one succeeded?
> >
> >> > Thanks
> >> >
> >> > --8<--
> >> >
> >> > Dmitry reported that sctp_add_bind_addr may read more bytes than
> >> > expected in case the parameter is a IPv4 addr supplied by the user
> >> > through calls such as sctp_bindx_add(), because it always copies
> >> > sizeof(union sctp_addr) while the buffer may be just a struct
> >> > sockaddr_in, which is smaller.
> >> >
> >> > This patch then fixes it by limiting the memcpy to the min between the
> >> > union size and a (new parameter) provided addr size. Where possible this
> >> > parameter still is the size of that union, except for reading from
> >> > user-provided buffers, which then it accounts for protocol type.
> >> >
> >> > Reported-by: Dmitry Vyukov <[email-masked]>
> >> > Signed-off-by: Marcelo Ricardo Leitner <[email-masked]>
> >> > ---
> >> >  include/net/sctp/structs.h |  2 +-
> >> >  net/sctp/bind_addr.c       | 14 ++++++++------
> >> >  net/sctp/protocol.c        |  1 +
> >> >  net/sctp/sm_make_chunk.c   |  2 +-
> >> >  net/sctp/socket.c          |  5 +++--
> >> >  5 files changed, 14 insertions(+), 10 deletions(-)
> >> >
> >> > diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> >> > index 20e72129be1ce0063eeafcbaadcee1f37e0c614c..97ba8a8c466f5c50bdc87ec578792e56553baa91 100644
> >> > --- a/include/net/sctp/structs.h
> >> > +++ b/include/net/sctp/structs.h
> >> > @@ -1099,7 +1099,7 @@ int sctp_bind_addr_dup(struct sctp_bind_addr *dest,
> >> >                         const struct sctp_bind_addr *src,
> >> >                         gfp_t gfp);
> >> >  int sctp_add_bind_addr(struct sctp_bind_addr *, union sctp_addr *,
> >> > -                      __u8 addr_state, gfp_t gfp);
> >> > +                      int new_size, __u8 addr_state, gfp_t gfp);
> >> >  int sctp_del_bind_addr(struct sctp_bind_addr *, union sctp_addr *);
> >> >  int sctp_bind_addr_match(struct sctp_bind_addr *, const union sctp_addr *,
> >> >                          struct sctp_sock *);
> >> > diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
> >> > index 871cdf9567e6bc9c13cb1077dc6866a67e6e4367..80129d10a0af9c33e7348b79d010b9e5e948e584 100644
> >> > --- a/net/sctp/bind_addr.c
> >> > +++ b/net/sctp/bind_addr.c
> >> > @@ -111,7 +111,8 @@ int sctp_bind_addr_dup(struct sctp_bind_addr *dest,
> >> >         dest->port = src->port;
> >> >
> >> >         list_for_each_entry(addr, &src->address_list, list) {
> >> > -               error = sctp_add_bind_addr(dest, &addr->a, 1, gfp);
> >> > +               error = sctp_add_bind_addr(dest, &addr->a, sizeof(addr->a),
> >> > +                                          1, gfp);
> >> >                 if (error < 0)
> >> >                         break;
> >> >         }
> >> > @@ -150,7 +151,7 @@ void sctp_bind_addr_free(struct sctp_bind_addr *bp)
> >> >
> >> >  /* Add an address to the bind address list in the SCTP_bind_addr structure. */
> >> >  int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
> >> > -                      __u8 addr_state, gfp_t gfp)
> >> > +                      int new_size, __u8 addr_state, gfp_t gfp)
> >> >  {
> >> >         struct sctp_sockaddr_entry *addr;
> >> >
> >> > @@ -159,7 +160,7 @@ int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
> >> >         if (!addr)
> >> >                 return -ENOMEM;
> >> >
> >> > -       memcpy(&addr->a, new, sizeof(*new));
> >> > +       memcpy(&addr->a, new, min_t(size_t, sizeof(*new), new_size));
> >> >
> >> >         /* Fix up the port if it has not yet been set.
> >> >          * Both v4 and v6 have the port at the same offset.
> >> > @@ -291,7 +292,8 @@ int sctp_raw_to_bind_addrs(struct sctp_bind_addr *bp, __u8 *raw_addr_list,
> >> >                 }
> >> >
> >> >                 af->from_addr_param(&addr, rawaddr, htons(port), 0);
> >> > -               retval = sctp_add_bind_addr(bp, &addr, SCTP_ADDR_SRC, gfp);
> >> > +               retval = sctp_add_bind_addr(bp, &addr, sizeof(addr),
> >> > +                                           SCTP_ADDR_SRC, gfp);
> >> >                 if (retval) {
> >> >                         /* Can't finish building the list, clean up. */
> >> >                         sctp_bind_addr_clean(bp);
> >> > @@ -453,8 +455,8 @@ static int sctp_copy_one_addr(struct net *net, struct sctp_bind_addr *dest,
> >> >                     (((AF_INET6 == addr->sa.sa_family) &&
> >> >                       (flags & SCTP_ADDR6_ALLOWED) &&
> >> >                       (flags & SCTP_ADDR6_PEERSUPP))))
> >> > -                       error = sctp_add_bind_addr(dest, addr, SCTP_ADDR_SRC,
> >> > -                                                   gfp);
> >> > +                       error = sctp_add_bind_addr(dest, addr, sizeof(addr),
> >> > +                                                  SCTP_ADDR_SRC, gfp);
> >> >         }
> >> >
> >> >         return error;
> >> > diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> >> > index ab0d538a74ed593571cfaef02cd1bb7ce872abe6..2fb609008311f51344704d82f21b4de9f08253da 100644
> >> > --- a/net/sctp/protocol.c
> >> > +++ b/net/sctp/protocol.c
> >> > @@ -214,6 +214,7 @@ int sctp_copy_local_addr_list(struct net *net, struct sctp_bind_addr *bp,
> >> >                               (copy_flags & SCTP_ADDR6_ALLOWED) &&
> >> >                               (copy_flags & SCTP_ADDR6_PEERSUPP)))) {
> >> >                                 error = sctp_add_bind_addr(bp, &addr->a,
> >> > +                                                   sizeof(addr->a),
> >> >                                                     SCTP_ADDR_SRC, GFP_ATOMIC);
> >> >                                 if (error)
> >> >                                         goto end_copy;
> >> > diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> >> > index 5d6a03fad3789a12290f5f14c5a7efa69c98f41a..1b91e9760fe514db6d89457e1d5da9e02800745e 100644
> >> > --- a/net/sctp/sm_make_chunk.c
> >> > +++ b/net/sctp/sm_make_chunk.c
> >> > @@ -1830,7 +1830,7 @@ no_hmac:
> >> >         /* Also, add the destination address. */
> >> >         if (list_empty(&retval->base.bind_addr.address_list)) {
> >> >                 sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest,
> >> > -                               SCTP_ADDR_SRC, GFP_ATOMIC);
> >> > +                                  sizeof(chunk->dest), SCTP_ADDR_SRC, GFP_ATOMIC);
> >> >         }
> >> >
> >> >         retval->next_tsn = retval->c.initial_tsn;
> >> > diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> >> > index 5ca2ebfe0be83882fcb841de6fa8029b6455ef85..213be3821a1d49e0c469c4ad4e9ff055a03205c5 100644
> >> > --- a/net/sctp/socket.c
> >> > +++ b/net/sctp/socket.c
> >> > @@ -386,7 +386,8 @@ static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
> >> >         /* Add the address to the bind address list.
> >> >          * Use GFP_ATOMIC since BHs will be disabled.
> >> >          */
> >> > -       ret = sctp_add_bind_addr(bp, addr, SCTP_ADDR_SRC, GFP_ATOMIC);
> >> > +       ret = sctp_add_bind_addr(bp, addr, af->sockaddr_len,
> >> > +                                SCTP_ADDR_SRC, GFP_ATOMIC);
> >> >
> >> >         /* Copy back into socket for getsockname() use. */
> >> >         if (!ret) {
> >> > @@ -576,7 +577,7 @@ static int sctp_send_asconf_add_ip(struct sock              *sk,
> >> >                         addr = addr_buf;
> >> >                         af = sctp_get_af_specific(addr->v4.sin_family);
> >> >                         memcpy(&saveaddr, addr, af->sockaddr_len);
> >> > -                       retval = sctp_add_bind_addr(bp, &saveaddr,
> >> > +                       retval = sctp_add_bind_addr(bp, &saveaddr, sizeof(saveaddr),
> >> >                                                     SCTP_ADDR_NEW, GFP_ATOMIC);
> >> >                         addr_buf += af->sockaddr_len;
> >> >                 }
> >> > --
> >> > 2.5.0
> >> >
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> >> the body of a message to [email-masked]
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to [email-masked]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>