sctp: fix copying more bytes than expected in sctp_add_bind_addr

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>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 6 deletions

diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index 871cdf9567e6..401c60750b20 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;