inet_diag: fix oops for IPv4 AF_INET6 TCP SYN-RECV state

Fix inet_diag to be aware of the fact that AF_INET6 TCP connections
instantiated for IPv4 traffic and in the SYN-RECV state were actually
created with inet_reqsk_alloc(), instead of inet6_reqsk_alloc(). This
means that for such connections inet6_rsk(req) returns a pointer to a
random spot in memory up to roughly 64KB beyond the end of the
request_sock.

With this bug, for a server using AF_INET6 TCP sockets and serving
IPv4 traffic, an inet_diag user like `ss state SYN-RECV` would lead to
inet_diag_fill_req() causing an oops or the export to user space of 16
bytes of kernel memory as a garbage IPv6 address, depending on where
the garbage inet6_rsk(req) pointed.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 14 deletions

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 0c34bfabc11f..16cfa42cfd99 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -44,6 +44,10 @@ struct inet_diag_entry {
         u16 dport;
         u16 family;
         u16 userlocks;
+#if IS_ENABLED(CONFIG_IPV6)
+        struct in6_addr saddr_storage;  /* for IPv4-mapped-IPv6 addresses */
+        struct in6_addr daddr_storage;  /* for IPv4-mapped-IPv6 addresses */
+#endif
 };
 
 static DEFINE_MUTEX(inet_diag_table_mutex);
@@ -596,6 +600,36 @@ static int inet_twsk_diag_dump(struct inet_timewait_sock *tw,
                                    cb->nlh->nlmsg_seq, NLM_F_MULTI, cb->nlh);
 }
 
+/* Get the IPv4, IPv6, or IPv4-mapped-IPv6 local and remote addresses
+ * from a request_sock. For IPv4-mapped-IPv6 we must map IPv4 to IPv6.
+ */
+static inline void inet_diag_req_addrs(const struct sock *sk,
+                                       const struct request_sock *req,
+                                       struct inet_diag_entry *entry)
+{
+        struct inet_request_sock *ireq = inet_rsk(req);
+
+#if IS_ENABLED(CONFIG_IPV6)
+        if (sk->sk_family == AF_INET6) {
+                if (req->rsk_ops->family == AF_INET6) {
+                        entry->saddr = inet6_rsk(req)->loc_addr.s6_addr32;
+                        entry->daddr = inet6_rsk(req)->rmt_addr.s6_addr32;
+                } else if (req->rsk_ops->family == AF_INET) {
+                        ipv6_addr_set_v4mapped(ireq->loc_addr,
+                                               &entry->saddr_storage);
+                        ipv6_addr_set_v4mapped(ireq->rmt_addr,
+                                               &entry->daddr_storage);
+                        entry->saddr = entry->saddr_storage.s6_addr32;
+                        entry->daddr = entry->daddr_storage.s6_addr32;
+                }
+        } else
+#endif
+        {
+                entry->saddr = &ireq->loc_addr;
+                entry->daddr = &ireq->rmt_addr;
+        }
+}
+
 static int inet_diag_fill_req(struct sk_buff *skb, struct sock *sk,
                               struct request_sock *req,
                               struct user_namespace *user_ns,
@@ -637,8 +671,10 @@ static int inet_diag_fill_req(struct sk_buff *skb, struct sock *sk,
         r->idiag_inode = 0;
 #if IS_ENABLED(CONFIG_IPV6)
         if (r->idiag_family == AF_INET6) {
-                *(struct in6_addr *)r->id.idiag_src = inet6_rsk(req)->loc_addr;
-                *(struct in6_addr *)r->id.idiag_dst = inet6_rsk(req)->rmt_addr;
+                struct inet_diag_entry entry;
+                inet_diag_req_addrs(sk, req, &entry);
+                memcpy(r->id.idiag_src, entry.saddr, sizeof(struct in6_addr));
+                memcpy(r->id.idiag_dst, entry.daddr, sizeof(struct in6_addr));
         }
 #endif
 
@@ -691,18 +727,7 @@ static int inet_diag_dump_reqs(struct sk_buff *skb, struct sock *sk,
                                 continue;
 
                         if (bc) {
-                                entry.saddr =
-#if IS_ENABLED(CONFIG_IPV6)
-                                        (entry.family == AF_INET6) ?
-                                        inet6_rsk(req)->loc_addr.s6_addr32 :
-#endif
-                                        &ireq->loc_addr;
-                                entry.daddr =
-#if IS_ENABLED(CONFIG_IPV6)
-                                        (entry.family == AF_INET6) ?
-                                        inet6_rsk(req)->rmt_addr.s6_addr32 :
-#endif
-                                        &ireq->rmt_addr;
+                                inet_diag_req_addrs(sk, req, &entry);
                                 entry.dport = ntohs(ireq->rmt_port);
 
                                 if (!inet_diag_bc_run(bc, &entry))