In the Linux kernel, the following vulnerability has been resolved:
RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference
MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT() links event_sub into sub_list before initializing the fields used by the shared error path.
If eventfd_ctx_fdget() then fails, the unwind path dereferences event_sub->ev_file in uverbs_uobject_put() and calls subscribe_event_xa_dealloc() with an unset xa_key_level1.
subscribe_event_xa_alloc() creates the XA entry exactly once for a given key_level1, on the first occurrence of that key. The unwind path must therefore call subscribe_event_xa_dealloc() exactly once for it as well.
Enforce that by adding devx_key_in_sub_list() and calling subscribe_event_xa_dealloc() only when the last matching pending entry is being cleaned up.
References
- https://git.kernel.org/stable/c/1025dc2f7ba29b04b8687790fa91f9cd1a53141e
- https://git.kernel.org/stable/c/43f8f7946814c8e5f464518246fdbc69b6e32326
- https://git.kernel.org/stable/c/5100febf8e9d6c8c5ba8dc6534c6a5e3376e5989
- https://git.kernel.org/stable/c/6e15b770461eeaa0ff73934922cb670a6a9db04e
- https://git.kernel.org/stable/c/78b9589fda266c71f0f9d0c858d4fa7381a890a5
- https://git.kernel.org/stable/c/7921821fc2b19c01588311f6e7468ae5b68b1f61
- https://git.kernel.org/stable/c/9be9aca28424228586fe9211c373ebdb826ebb6c
- https://git.kernel.org/stable/c/f345e744b6b087188cde2377da5cbe9713b61353