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.

Fixes: 759738537142 ("IB/mlx5: Enable subscription for device events over DEVX")
Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
Link: https://patch.msgid.link/20260428224319.37682-1-prathameshdeshpande7@gmail.com
Reviewed-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

0 files changed, 0 insertions, 0 deletions