inet_diag: avoid unsafe and nonsensical prefix matches in inet_diag_bc_run()

Add logic to check the address family of the user-supplied conditional
and the address family of the connection entry. We now do not do
prefix matching of addresses from different address families (AF_INET
vs AF_INET6), except for the previously existing support for having an
IPv4 prefix match an IPv4-mapped IPv6 address (which this commit
maintains as-is).

This change is needed for two reasons:

(1) The addresses are different lengths, so comparing a 128-bit IPv6
prefix match condition to a 32-bit IPv4 connection address can cause
us to unwittingly walk off the end of the IPv4 address and read
garbage or oops.

(2) The IPv4 and IPv6 address spaces are semantically distinct, so a
simple bit-wise comparison of the prefixes is not meaningful, and
would lead to bogus results (except for the IPv4-mapped IPv6 case,
which this commit maintains).

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

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 529747d07a2a5be8e37b378bae7caf325236a709..95f1a458371df36c62f0ff7f1e44545dbda97866 100644 (file)
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -432,25 +432,31 @@ static int inet_diag_bc_run(const struct nlattr *_bc,
                                break;
                        }
 
-                       if (cond->prefix_len == 0)
-                               break;
-
                        if (op->code == INET_DIAG_BC_S_COND)
                                addr = entry->saddr;
                        else
                                addr = entry->daddr;
 
+                       if (cond->family != AF_UNSPEC &&
+                           cond->family != entry->family) {
+                               if (entry->family == AF_INET6 &&
+                                   cond->family == AF_INET) {
+                                       if (addr[0] == 0 && addr[1] == 0 &&
+                                           addr[2] == htonl(0xffff) &&
+                                           bitstring_match(addr + 3,
+                                                           cond->addr,
+                                                           cond->prefix_len))
+                                               break;
+                               }
+                               yes = 0;
+                               break;
+                       }
+
+                       if (cond->prefix_len == 0)
+                               break;
                        if (bitstring_match(addr, cond->addr,
                                            cond->prefix_len))
                                break;
-                       if (entry->family == AF_INET6 &&
-                           cond->family == AF_INET) {
-                               if (addr[0] == 0 && addr[1] == 0 &&
-                                   addr[2] == htonl(0xffff) &&
-                                   bitstring_match(addr + 3, cond->addr,
-                                                   cond->prefix_len))
-                                       break;
-                       }
                        yes = 0;
                        break;
                }