inet_diag: validate byte code to prevent oops in inet_diag_bc_run()

Add logic to validate INET_DIAG_BC_S_COND and INET_DIAG_BC_D_COND
operations.

Previously we did not validate the inet_diag_hostcond, address family,
address length, and prefix length. So a malicious user could make the
kernel read beyond the end of the bytecode array by claiming to have a
whole inet_diag_hostcond when the bytecode was not long enough to
contain a whole inet_diag_hostcond of the given address family. Or
they could make the kernel read up to about 27 bytes beyond the end of
a connection address by passing a prefix length that exceeded the
length of addresses of the given family.

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 16cfa42cfd992b06d19527906a61be9238767f0f..529747d07a2a5be8e37b378bae7caf325236a709 100644 (file)
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -513,6 +513,44 @@ static int valid_cc(const void *bc, int len, int cc)
        return 0;
 }
 
+/* Validate an inet_diag_hostcond. */
+static bool valid_hostcond(const struct inet_diag_bc_op *op, int len,
+                          int *min_len)
+{
+       int addr_len;
+       struct inet_diag_hostcond *cond;
+
+       /* Check hostcond space. */
+       *min_len += sizeof(struct inet_diag_hostcond);
+       if (len < *min_len)
+               return false;
+       cond = (struct inet_diag_hostcond *)(op + 1);
+
+       /* Check address family and address length. */
+       switch (cond->family) {
+       case AF_UNSPEC:
+               addr_len = 0;
+               break;
+       case AF_INET:
+               addr_len = sizeof(struct in_addr);
+               break;
+       case AF_INET6:
+               addr_len = sizeof(struct in6_addr);
+               break;
+       default:
+               return false;
+       }
+       *min_len += addr_len;
+       if (len < *min_len)
+               return false;
+
+       /* Check prefix length (in bits) vs address length (in bytes). */
+       if (cond->prefix_len > 8 * addr_len)
+               return false;
+
+       return true;
+}
+
 static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
 {
        const void *bc = bytecode;
@@ -520,18 +558,22 @@ static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
 
        while (len > 0) {
                const struct inet_diag_bc_op *op = bc;
+               int min_len = sizeof(struct inet_diag_bc_op);
 
 //printk("BC: %d %d %d {%d} / %d\n", op->code, op->yes, op->no, op[1].no, len);
                switch (op->code) {
-               case INET_DIAG_BC_AUTO:
                case INET_DIAG_BC_S_COND:
                case INET_DIAG_BC_D_COND:
+                       if (!valid_hostcond(bc, len, &min_len))
+                               return -EINVAL;
+                       /* fall through */
+               case INET_DIAG_BC_AUTO:
                case INET_DIAG_BC_S_GE:
                case INET_DIAG_BC_S_LE:
                case INET_DIAG_BC_D_GE:
                case INET_DIAG_BC_D_LE:
                case INET_DIAG_BC_JMP:
-                       if (op->no < 4 || op->no > len + 4 || op->no & 3)
+                       if (op->no < min_len || op->no > len + 4 || op->no & 3)
                                return -EINVAL;
                        if (op->no < len &&
                            !valid_cc(bytecode, bytecode_len, len - op->no))
@@ -542,7 +584,7 @@ static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
                default:
                        return -EINVAL;
                }
-               if (op->yes < 4 || op->yes > len + 4 || op->yes & 3)
+               if (op->yes < min_len || op->yes > len + 4 || op->yes & 3)
                        return -EINVAL;
                bc  += op->yes;
                len -= op->yes;