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

From: Dmitry Vyukov
Date: Tue Jan 26 2016 - 08:29:18 EST

On Mon, Jan 25, 2016 at 6:52 PM, Marcelo Ricardo Leitner
<marcelo.leitner@xxxxxxxxx> wrote:
> Great. Dmitry, please give this a run. Local tests looked good but who
> knows what syzkaller may find.

Now running with this patch.

> 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 <dvyukov@xxxxxxxxxx>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> ---
> 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
>