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

Overview

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 exhausted\n");
	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)

Affected

• Linux >= efa78f2ae363428525fb4981bb63c555ee79f3c7 < efebc23e9b29e3e5a9e2127dd066929f7f0d315e
• Linux >= 833ecd0eae76eadf81d6d747bb5bc992d1151867 < 8d6f26d48e61ef34f1921289401dbf36b10816af
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < 82f59aa27f33bd014a7d8739371ab5712d15e33b
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < b07d87b31631edb6529e6cdcca790a7489d1250d
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < dd29891ed840f6b8d020b759d0dc4a00b1d6e4ea
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < 5f5a41a48dbf9eda57b67ce23e548602cf7195a6
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < f9596b1566616a8be0592dbceccb6344a7c6f6bb
• Linux >= 00aff3590fc0a73bddd3b743863c14e76fd35c0c < ba0533fc163f905fe817cfabdf8ed4058da44800
• Linux 638fa20b618b2bbcf86da71231624cc82121a036
• Linux 7bc9e7f70bc57d8f02ffea2a42094281effb15ef
• Linux ef488669b2652bde5b6ee5a409a5b048a2a50db4
• Linux 4919d82f7041157a421ca9bf39a78551d5ad8a1b
• Linux 3b2957fc09fe1ac7f07f40dd50dd5f93e3f3a7a2
• Linux >= 5.10.132 < 5.10.265
• Linux >= 5.15.56 < 5.15.216
• Linux >= 4.9.324 < 4.10
• Linux >= 4.14.289 < 4.15
• Linux >= 4.19.253 < 4.20
• Linux >= 5.4.207 < 5.5
• Linux >= 5.18.13 < 5.19
• Linux 5.19

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.