Overview
About vulnerability
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.
Details
- Affected product:
- Debian 11 ELS
- Affected packages:
- linux @ 5.10.269
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| Debian 12 | Planned | — |
| Debian 13 | Released |
15 kernels
|