CVE-2026-74493

Summary

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 Software

Weaknesses

References

• 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

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