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[81.108.45.148]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-447b3d47ff1sm1073294f8f.6.2026.04.28.15.43.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 15:43:39 -0700 (PDT) From: Prathamesh Deshpande To: jgg@ziepe.ca, leon@kernel.org Cc: yishaih@nvidia.com, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Prathamesh Deshpande Subject: [PATCH v2] RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference Date: Tue, 28 Apr 2026 23:42:49 +0100 Message-ID: <20260428224319.37682-1-prathameshdeshpande7@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- v2: - fix duplicate-key unwind by deallocating each XA entry only once - add devx_key_in_sub_list() to detect the last matching pending entry - keep event_sub->ev_file and xa_key_level1 initialization before sub_list insertion - update commit message to explain the duplicate-key unwind rule drivers/infiniband/hw/mlx5/devx.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/drivers/infiniband/hw/mlx5/devx.c b/drivers/infiniband/hw/mlx5/devx.c index 645ebcc0832d..c2ae5a140471 100644 --- a/drivers/infiniband/hw/mlx5/devx.c +++ b/drivers/infiniband/hw/mlx5/devx.c @@ -1913,6 +1913,17 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_OBJ_ASYNC_QUERY)( return err; } +static bool devx_key_in_sub_list(struct list_head *list, u32 key_level1) +{ + struct devx_event_subscription *s; + + list_for_each_entry(s, list, event_list) + if (s->xa_key_level1 == key_level1) + return true; + + return false; +} + static void subscribe_event_xa_dealloc(struct mlx5_devx_event_table *devx_event_table, u32 key_level1, @@ -2160,10 +2171,17 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( event_sub = kzalloc_obj(*event_sub); if (!event_sub) { + if (!devx_key_in_sub_list(&sub_list, key_level1)) + subscribe_event_xa_dealloc(devx_event_table, + key_level1, + obj, + obj_id); err = -ENOMEM; goto err; } + event_sub->ev_file = ev_file; + event_sub->xa_key_level1 = key_level1; list_add_tail(&event_sub->event_list, &sub_list); uverbs_uobject_get(&ev_file->uobj); if (use_eventfd) { @@ -2178,9 +2196,6 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( } event_sub->cookie = cookie; - event_sub->ev_file = ev_file; - /* May be needed upon cleanup the devx object/subscription */ - event_sub->xa_key_level1 = key_level1; event_sub->xa_key_level2 = obj_id; INIT_LIST_HEAD(&event_sub->obj_list); } @@ -2225,10 +2240,11 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( list_for_each_entry_safe(event_sub, tmp_sub, &sub_list, event_list) { list_del(&event_sub->event_list); - subscribe_event_xa_dealloc(devx_event_table, - event_sub->xa_key_level1, - obj, - obj_id); + if (!devx_key_in_sub_list(&sub_list, event_sub->xa_key_level1)) + subscribe_event_xa_dealloc(devx_event_table, + event_sub->xa_key_level1, + obj, + obj_id); if (event_sub->eventfd) eventfd_ctx_put(event_sub->eventfd); -- 2.43.0