The tipc_msg_build() function in net/tipc/msg.c is written in such a way as to create a highly exploitable kernel heap overflow that would allow a local user to escalate privileges to root by issuing maliciously crafted sendmsg() calls. At a minimum, the following issues should be fixed: 1. The tipc_msg_calc_data_size() function is almost totally broken. It sums together size_t values (iov_lens), but returns an integer. Two things can go wrong - the total value can wrap around, or on 64-bit platforms, iov_len values greater than UINT_MAX will be truncated. 2. The comparison of dsz to TIPC_MAX_USER_MSG_SIZE is signed, so negative (large unsigned) values will pass this check. 3. The comparison of sz to max_size is also signed. As a result of these issues, it's possible to cause the allocation of a small heap buffer and the subsequent copying of a carefully controlled larger amount of data into that buffer. I haven't found a Linux distribution that defines a module alias for TIPC (even though most compile it as a module), so an administrator will have had to explicitly load the TIPC module for a system to be vulnerable. -Dan