Re: net/sctp: out-of-bounds access in sctp_add_bind_addr

[Marcelo Ricardo Leitner]

Something like this. Builds, but UNTESTED.
Uses union sizeof where possible but when reading from a buffer that is
not aligned to it, like that user supplied one. Then relies on
af->sockaddr_len

--8<--

---
 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 9bb80ec4c08ff06f6e629078c5a926c3def3ce23..3765f1fd06aac253ec5ee8e8bd18fffefda64d62 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