CVE-2026-74692net/smc: fix TOCTOU race between smc_listen_out() and listener close

Official description

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix TOCTOU race between smc_listen_out() and listener close smc_listen_out() reads lsmc->sk.sk_state without the listener lock, then acquires lock_sock_nested() only after the check passes. This opens a window where smc_close_active() can transition the listener to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept queue, and release the lock, all between the lockless read and the delayed lock acquisition: smc_listen_work (smc_hs_wq) smc_close_active() ------------------------------- ------------------------- release_sock(child) if (sk_state == SMC_LISTEN) TRUE lock_sock(listener) sk_state = SMC_CLOSED smc_close_cleanup_listen() release_sock(listener) flush_work(tcp_listen_work) lock_sock_nested(listener) smc_accept_enqueue(listener, child) /* child enqueued on dead listener */ smc_close_active() flushes only tcp_listen_work. Work items already dispatched onto smc_hs_wq for the CLC handshake continue running unguarded. smc_accept_enqueue() takes a sock_hold() on the child that is never released, so the child smc_sock, its clcsock, and the reference all leak. A remote peer that opens TCP connections while the server calls close() can exhaust kernel memory. Move lock_sock_nested() to before the sk_state check so that the test and the enqueue are atomic under the listener lock.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa
• https://git.kernel.org/stable/c/feb71634bb1abab3e8fb5cde874b27001cc1282e
• https://git.kernel.org/stable/c/01865e1ddb126b25ac9eba5cdd7ec49e11183a64
• https://git.kernel.org/stable/c/00f89433777236ced4771211047fb5d4cd581cea
• https://git.kernel.org/stable/c/78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67
• https://git.kernel.org/stable/c/ff5bcd804b5bc5c64736b7d318c20e12ea9506b8
• https://git.kernel.org/stable/c/185a4caeecabc150106deda1da170b09f2ad803f