CVE-2026-74493net/smc: fix socket use-after-free during link group termination

Official description

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix socket use-after-free during link group termination __smc_lgr_terminate() drops conns_lock after finding a connection in lgr->conns_all, but before taking a reference on its socket. The connection is embedded in the socket, and its registration reference protects it only while the connection remains in the tree. A concurrent close can unregister the connection and drop that reference, freeing the socket before the termination worker reaches sock_hold(). The race is reachable when close overlaps link group termination. Local stress testing reproduced the use-after-free and KASAN reported: BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc] Write of size 4 by task kworker/3:3 Workqueue: events smc_lgr_terminate_work [smc] __smc_lgr_terminate.part.0 [smc] The socket was allocated by smc_create(), freed through slab_free_after_rcu_debug(), and was followed by: refcount_t: addition on 0; use-after-free. __smc_lgr_terminate.part.0 [smc] Take the socket reference while conns_lock still protects the tree entry. The unregister path then cannot drop the last reference until termination has finished using the socket.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ff44f2df57fb5560bdc75eb977867643e764a262
• https://git.kernel.org/stable/c/9fb17c95b8f0683570fca1fb2792264147af937a
• https://git.kernel.org/stable/c/bea8dc14de2d56aca749d368563e6888217710a5
• https://git.kernel.org/stable/c/5a42f162b857019a4c10ff687dc3bcdf51831865
• https://git.kernel.org/stable/c/281c103a8eaed59001ce952f231df1b07674215a
• https://git.kernel.org/stable/c/f807a63d0d95680c34f677700da9148a07d7c78f
• https://git.kernel.org/stable/c/f0541a775d04c88e90ba448e35ce0d743512822a
• https://git.kernel.org/stable/c/f621d6ebeebb6374342571e4ddf45fdbc420f6cd