CVE-2026-68117

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

tipc: clear sock->sk on the failed-insert path in tipc_sk_create()

When tipc_sk_create() fails to insert the new socket (tipc_sk_insert() returns non-zero), its error path frees the sk with sk_free() but leaves sock->sk pointing at the freed object:

if (tipc_sk_insert(tsk)) {
	sk_free(sk);
	pr_warn(Socket create failed; port number exhaustedn);
	return -EINVAL;
}

This is harmless for plain socket(): the syscall layer clears sock->ops before releasing, so tipc_release() is never called. It is not harmless on the accept() path. tipc_accept() creates the pre-allocated child socket with tipc_sk_create(net, new_sock, 0, kern); on failure it leaves new_sock->sk dangling and new_sock->ops non-NULL, and do_accept() then fput()s the new file, so __sock_release() -> tipc_release() runs lock_sock(new_sock->sk) on the freed sk – a use-after-free write of the sk_lock spinlock.

tipc_release() already guards this exact failed accept() releases a pre-allocated child case with if (sk == NULL) return 0;, but the guard is bypassed because tipc_sk_create() left sock->sk non-NULL (dangling) rather than NULL.

Clear sock->sk on the failed-insert path so the existing tipc_release() NULL check fires and the use-after-free is avoided.

The tipc_sk_insert() failure is reached when the per-netns socket rhashtable hits its max_size (tsk_rht_params.max_size = 1048576, ~2M elements) – i.e. once a netns holds ~2M TIPC sockets every insert returns -E2BIG.

BUG: KASAN: slab-use-after-free in lock_sock_nested (net/core/sock.c:3839) Write of size 8 at addr ffff8880047cdc38 by task init/1 lock_sock_nested (net/core/sock.c:3839) tipc_release (net/tipc/socket.c:638) __sock_release (net/socket.c:710) sock_close (net/socket.c:1501) __fput (fs/file_table.c:512) Allocated by task 1: sk_alloc (net/core/sock.c:2308) tipc_sk_create (net/tipc/socket.c:487) tipc_accept (net/tipc/socket.c:2744) do_accept (net/socket.c:2034) Freed by task 1: __sk_destruct (net/core/sock.c:2391) tipc_sk_create (net/tipc/socket.c:504) tipc_accept (net/tipc/socket.c:2744) do_accept (net/socket.c:2034)

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/5f5a41a48dbf9eda57b67ce23e548602cf7195a6
• https://git.kernel.org/stable/c/82f59aa27f33bd014a7d8739371ab5712d15e33b
• https://git.kernel.org/stable/c/8d6f26d48e61ef34f1921289401dbf36b10816af
• https://git.kernel.org/stable/c/b07d87b31631edb6529e6cdcca790a7489d1250d
• https://git.kernel.org/stable/c/ba0533fc163f905fe817cfabdf8ed4058da44800
• https://git.kernel.org/stable/c/dd29891ed840f6b8d020b759d0dc4a00b1d6e4ea
• https://git.kernel.org/stable/c/efebc23e9b29e3e5a9e2127dd066929f7f0d315e
• https://git.kernel.org/stable/c/f9596b1566616a8be0592dbceccb6344a7c6f6bb