sctp: fail if no bound addresses can be used for a given scope

[ Upstream commit 458e279f861d3f61796894cd158b780765a1569f ]

Currently, if you bind the socket to something like:
        servaddr.sin6_family = AF_INET6;
        servaddr.sin6_port = htons(0);
        servaddr.sin6_scope_id = 0;
        inet_pton(AF_INET6, "::1", &servaddr.sin6_addr);

And then request a connect to:
        connaddr.sin6_family = AF_INET6;
        connaddr.sin6_port = htons(20000);
        connaddr.sin6_scope_id = if_nametoindex("lo");
        inet_pton(AF_INET6, "fe88::1", &connaddr.sin6_addr);

What the stack does is:
 - bind the socket
 - create a new asoc
 - to handle the connect
   - copy the addresses that can be used for the given scope
   - try to connect

But the copy returns 0 addresses, and the effect is that it ends up
trying to connect as if the socket wasn't bound, which is not the
desired behavior. This unexpected behavior also allows KASLR leaks
through SCTP diag interface.

The fix here then is, if when trying to copy the addresses that can
be used for the scope used in connect() it returns 0 addresses, bail
out. This is what TCP does with a similar reproducer.

Reported-by: Pietro Borrello <borrello@diag.uniroma1.it>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/9fcd182f1099f86c6661f3717f63712ddd1c676c.1674496737.git.marcelo.leitner@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index a825e74d01fca894f27aed84f4f4838692a1fe35..614bc081ca50182c762d6330a6a6f3aa1a74913d 100644 (file)
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c
@@ -73,6 +73,12 @@ int sctp_bind_addr_copy(struct net *net, struct sctp_bind_addr *dest,
                }
        }
 
+       /* If somehow no addresses were found that can be used with this
+        * scope, it's an error.
+        */
+       if (list_empty(&dest->address_list))
+               error = -ENETUNREACH;
+
 out:
        if (error)
                sctp_bind_addr_clean(dest);