RDMA/rtrs: Fix KASAN: stack-out-of-bounds bug

When KASAN is enabled, we notice warning below:
[  483.436975] ==================================================================
[  483.437234] BUG: KASAN: stack-out-of-bounds in _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.437430] Read of size 4 at addr ffff88a195fd7d30 by task kworker/1:3/6954

[  483.437731] CPU: 1 PID: 6954 Comm: kworker/1:3 Kdump: loaded Tainted: G           O      5.4.82-pserver #5.4.82-1+feature+linux+5.4.y+dbg+20201210.1532+987e7a6~deb10
[  483.437976] Hardware name: Supermicro Super Server/X11DDW-L, BIOS 3.3 02/21/2020
[  483.438168] Workqueue: rtrs_server_wq hb_work [rtrs_core]
[  483.438323] Call Trace:
[  483.438486]  dump_stack+0x96/0xe0
[  483.438646]  ? _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.438802]  print_address_description.constprop.6+0x1b/0x220
[  483.438966]  ? _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.439133]  ? _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.439285]  __kasan_report.cold.9+0x1a/0x32
[  483.439444]  ? _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.439597]  kasan_report+0x10/0x20
[  483.439752]  _mlx5_ib_post_send+0x188a/0x2560 [mlx5_ib]
[  483.439910]  ? update_sd_lb_stats+0xfb1/0xfc0
[  483.440073]  ? set_reg_wr+0x520/0x520 [mlx5_ib]
[  483.440222]  ? update_group_capacity+0x340/0x340
[  483.440377]  ? find_busiest_group+0x314/0x870
[  483.440526]  ? update_sd_lb_stats+0xfc0/0xfc0
[  483.440683]  ? __bitmap_and+0x6f/0x100
[  483.440832]  ? __lock_acquire+0xa2/0x2150
[  483.440979]  ? __lock_acquire+0xa2/0x2150
[  483.441128]  ? __lock_acquire+0xa2/0x2150
[  483.441279]  ? debug_lockdep_rcu_enabled+0x23/0x60
[  483.441430]  ? lock_downgrade+0x390/0x390
[  483.441582]  ? __lock_acquire+0xa2/0x2150
[  483.441729]  ? __lock_acquire+0xa2/0x2150
[  483.441876]  ? newidle_balance+0x425/0x8f0
[  483.442024]  ? __lock_acquire+0xa2/0x2150
[  483.442172]  ? debug_lockdep_rcu_enabled+0x23/0x60
[  483.442330]  hb_work+0x15d/0x1d0 [rtrs_core]
[  483.442479]  ? schedule_hb+0x50/0x50 [rtrs_core]
[  483.442627]  ? lock_downgrade+0x390/0x390
[  483.442781]  ? process_one_work+0x40d/0xa50
[  483.442931]  process_one_work+0x4ee/0xa50
[  483.443082]  ? pwq_dec_nr_in_flight+0x110/0x110
[  483.443231]  ? do_raw_spin_lock+0x119/0x1d0
[  483.443383]  worker_thread+0x65/0x5c0
[  483.443532]  ? process_one_work+0xa50/0xa50
[  483.451839]  kthread+0x1e2/0x200
[  483.451983]  ? kthread_create_on_node+0xc0/0xc0
[  483.452139]  ret_from_fork+0x3a/0x50

The problem is we use wrong type when send wr, hw driver expect the type
of IB_WR_RDMA_WRITE_WITH_IMM wr should be ib_rdma_wr, and doing
container_of to access member. The fix is simple use ib_rdma_wr instread
of ib_send_wr.

Fixes: c0894b3ea6 ("RDMA/rtrs: core: lib functions shared between client and server modules")
Link: https://lore.kernel.org/r/20201217141915.56989-20-jinpu.wang@cloud.ionos.com
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs.c

@@ -182,16 +182,16 @@ int rtrs_post_rdma_write_imm_empty(struct rtrs_con *con, struct ib_cqe *cqe,
 				    u32 imm_data, enum ib_send_flags flags,
 				    struct ib_send_wr *head)
 {
-	struct ib_send_wr wr;
+	struct ib_rdma_wr wr;
 
-	wr = (struct ib_send_wr) {
-		.wr_cqe	= cqe,
-		.send_flags	= flags,
-		.opcode	= IB_WR_RDMA_WRITE_WITH_IMM,
-		.ex.imm_data	= cpu_to_be32(imm_data),
+	wr = (struct ib_rdma_wr) {
+		.wr.wr_cqe	= cqe,
+		.wr.send_flags	= flags,
+		.wr.opcode	= IB_WR_RDMA_WRITE_WITH_IMM,
+		.wr.ex.imm_data	= cpu_to_be32(imm_data),
 	};
 
-	return rtrs_post_send(con->qp, head, &wr);
+	return rtrs_post_send(con->qp, head, &wr.wr);
 }
 EXPORT_SYMBOL_GPL(rtrs_post_rdma_write_imm_empty);