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>

1 files changed, 45 insertions, 3 deletions

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 16cfa42cfd99..529747d07a2a 100644
--- 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;