SUNRPC: pin upper rpc_clnt across the TLS connect_worker
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: total
Summary
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: pin upper rpc_clnt across the TLS connect_worker The TLS connect path has a use-after-free: nothing pins the upper rpc_clnt across the delayed connect_worker. xs_connect() stores task->tk_client in sock_xprt::clnt as a raw pointer and queues the worker; for TLS-secured transports that worker is xs_tcp_tls_setup_socket(), which reads several fields out of the saved pointer (cl_timeout, cl_program, cl_prog, cl_vers, cl_cred, cl_stats) to construct the args for the inner handshake rpc_clnt. The xprt does not reference the rpc_clnt; the rpc_clnt references the xprt. xs_destroy() does cancel the connect_worker, but it runs only when the xprt's refcount drops to zero, which cannot happen until the rpc_clnt releases its cl_xprt reference in rpc_free_client_work(). When a TLS handshake fails fatally (for example, an mTLS mount whose client cert does not match the server), the connecting task is woken with -EACCES and exits, the mount caller invokes rpc_shutdown_client(), and the upper rpc_clnt is freed before the queued connect_worker fires. xs_tcp_tls_setup_socket() then dereferences the freed clnt, producing the refcount_t underflow Michael Nemanov reported. Take a reference on the upper rpc_clnt in xs_connect() for TLS transports via a new rpc_hold_client() helper, and drop it in the connect_worker's exit path with rpc_release_client(). The xprt_lock_connect() / xprt_unlock_connect() pairing already serialises xs_connect() with xs_tcp_tls_setup_socket(), so the take and release are balanced one-for-one. The non-TLS connect worker (xs_tcp_setup_socket) never reads sock_xprt::clnt, so leave that path alone and avoid the clnt-holds-xprt-holds-clnt cycle that would otherwise prevent xprt destruction.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: total
- Record last updated
Affected versions
- Linux Linux
From 75eb6af7acdf566c68d61e98e67ee2f235201c02 · fixed in 79cd550f8c884523b604fbfa43eb02def74d6224; From 75eb6af7acdf566c68d61e98e67ee2f235201c02 · fixed in 7a65b41b657b71d5a77861f47dd13eb4bc8e10d0; From 75eb6af7acdf566c68d61e98e67ee2f235201c02 · fixed in 5b0427ba582d143a364301f825f4e32272f06d2d; From 75eb6af7acdf566c68d61e98e67ee2f235201c02 · fixed in d49f6d098ed48775b9d27a9f9c5c220fdf76f102; From 75eb6af7acdf566c68d61e98e67ee2f235201c02 · fixed in 46bc86c833956219bbfd246c1ffd832a479c5199
- Linux Linux
6.5
- KernelLinux
From 6.5.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5