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

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
[off-list ref] wrote:

quoted

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?

quoted

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@google.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
 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

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