RDMA/ucma: Fix use after free in destroy id flow

ucma_free_ctx() should call to __destroy_id() on all the connection requests
that have not been delivered to user space. Currently it calls on the
context itself and cause to use after free.

Fixes the trace:

   BUG: Unable to handle kernel data access on write at 0x5deadbeef0000108
   Faulting instruction address: 0xc0080000002428f4
   Oops: Kernel access of bad area, sig: 11 [#1]
   Call Trace:
   [c000000207f2b680] [c00800000024280c] .__destroy_id+0x28c/0x610 [rdma_ucm] (unreliable)
   [c000000207f2b750] [c0080000002429c4] .__destroy_id+0x444/0x610 [rdma_ucm]
   [c000000207f2b820] [c008000000242c24] .ucma_close+0x94/0xf0 [rdma_ucm]
   [c000000207f2b8c0] [c00000000046fbdc] .__fput+0xac/0x330
   [c000000207f2b960] [c00000000015d48c] .task_work_run+0xbc/0x110
   [c000000207f2b9f0] [c00000000012fb00] .do_exit+0x430/0xc50
   [c000000207f2bae0] [c0000000001303ec] .do_group_exit+0x5c/0xd0
   [c000000207f2bb70] [c000000000144a34] .get_signal+0x194/0xe30
   [c000000207f2bc60] [c00000000001f6b4] .do_notify_resume+0x124/0x470
   [c000000207f2bd60] [c000000000032484] .interrupt_exit_user_prepare+0x1b4/0x240
   [c000000207f2be20] [c000000000010034] interrupt_return+0x14/0x1c0

Rename listen_ctx to conn_req_ctx as the poor name was the cause of this
bug.

Fixes: a1d33b7 ("RDMA/ucma: Rework how new connections are passed through event delivery")
Link: https://lore.kernel.org/r/20201012045600.418271-4-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: maorgottlieb

drivers/infiniband/core/ucma.c

@@ -112,7 +112,7 @@ struct ucma_multicast {
 
 struct ucma_event {
 	struct ucma_context	*ctx;
-	struct ucma_context	*listen_ctx;
+	struct ucma_context	*conn_req_ctx;
 	struct ucma_multicast	*mc;
 	struct list_head	list;
 	struct rdma_ucm_event_resp resp;
@@ -308,7 +308,7 @@ static int ucma_connect_event_handler(struct rdma_cm_id *cm_id,
 	uevent = ucma_create_uevent(listen_ctx, event);
 	if (!uevent)
 		goto err_alloc;
-	uevent->listen_ctx = listen_ctx;
+	uevent->conn_req_ctx = ctx;
 	uevent->resp.id = ctx->id;
 
 	ctx->cm_id->context = ctx;
@@ -534,7 +534,7 @@ static int ucma_free_ctx(struct ucma_context *ctx)
 	/* Cleanup events not yet reported to the user. */
 	mutex_lock(&ctx->file->mut);
 	list_for_each_entry_safe(uevent, tmp, &ctx->file->event_list, list) {
-		if (uevent->ctx == ctx || uevent->listen_ctx == ctx)
+		if (uevent->ctx == ctx || uevent->conn_req_ctx == ctx)
 			list_move_tail(&uevent->list, &list);
 	}
 	list_del(&ctx->list);
@@ -548,8 +548,9 @@ static int ucma_free_ctx(struct ucma_context *ctx)
 	 */
 	list_for_each_entry_safe(uevent, tmp, &list, list) {
 		list_del(&uevent->list);
-		if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST)
-			__destroy_id(uevent->ctx);
+		if (uevent->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST &&
+		    uevent->conn_req_ctx != ctx)
+			__destroy_id(uevent->conn_req_ctx);
 		kfree(uevent);
 	}