Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

smc: Fix various oops due to inet_sock type confusion.

syzbot reported weird splats [0][1] in cipso_v4_sock_setattr() while freeing inet_sk(sk)->inet_opt.

The address was freed multiple times even though it was read-only memory.

cipso_v4_sock_setattr() did nothing wrong, and the root cause was type confusion.

The cited commit made it possible to create smc_sock as an INET socket.

The issue is that struct smc_sock does not have struct inet_sock as the first member but hijacks AF_INET and AF_INET6 sk_family, which confuses various places.

In this case, inet_sock.inet_opt was actually smc_sock.clcsk_data_ready(), which is an address of a function in the text segment.

$ pahole -C inet_sock vmlinux struct inet_sock { ... struct ip_options_rcu * inet_opt; /* 784 8 */

$ pahole -C smc_sock vmlinux struct smc_sock { ... void (*clcsk_data_ready)(struct sock *); /* 784 8 */

The same issue for another field was reported before. [2][3]

At that time, an ugly hack was suggested [4], but it makes both INET and SMC code error-prone and hard to change.

Also, yet another variant was fixed by a hacky commit 98d4435efcbf3 ("net/smc: prevent NULL pointer dereference in txopt_get").

Instead of papering over the root cause by such hacks, we should not allow non-INET socket to reuse the INET infra.

Let's add inet_sock as the first member o…