[PATCH for-next 3/3] RDMA/rtrs: Avoid use-after-free in rtrs_clt_rdma_cm_handler

[Li Zhijian]

Currently, con will be destroyed when wait_event_interruptible_timeout()
returns ERESTARTSYS. But the in-flight event handler
rtrs_clt_rdma_cm_handler() could be rescheduled/wakeup which
may cause a use-after-free.

    WARNING: CPU: 0 PID: 14766 at drivers/infiniband/ulp/rtrs/rtrs-clt.c:1687 rtrs_clt_rdma_cm_handler+0x620/0x640 [rtrs_client]
     Modules linked in: rnbd_client rtrs_client rtrs_core rdma_cm iw_cm ib_cm rdma_rxe ib_uverbs ib_core libiscsi scsi_transport_iscsi crc32_generic udp_tunnel dax_pmem nd_pmem nd_btt virtiofs crc32c_intel nvme fuse nvme_core nfit
libnvdimm dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_mirror dm_region_hash dm_log dm_mod [last unloaded: ib_core]
     CPU: 0 PID: 14766 Comm: kworker/u2:3 Kdump: loaded Tainted: G        W          6.2.0-rc6-roce-flush+ #56
     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
     Workqueue: ib_addr process_one_req [ib_core]
     RIP: 0010:rtrs_clt_rdma_cm_handler+0x620/0x640 [rtrs_client]
     Code: 00 0f 85 5f fd ff ff 4c 8b 23 41 bd f4 ff ff ff e9 95 fb ff ff 0f 0b 4c 89 f7 41 bd ea ff ff ff e8 75 c8 92 ec e9 4b ff ff ff <0f> 0b 4c 89 f7 41 bd ea ff ff ff e8 60 c8 92 ec e9 36 ff ff ff e8
     RSP: 0018:ffffa4ef41cdbc60 EFLAGS: 00010246
     RAX: 0000000000000000 RBX: ffff9372c394e600 RCX: 0000000000000001
     RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffad634277
     RBP: ffffa4ef41cdbd00 R08: 0000000000000000 R09: 0000000000000001
     R10: 0000000000003ff3 R11: 0000000000000000 R12: ffff9372c3164800
     R13: ffff9372c3164800 R14: ffff9372c394e640 R15: ffff9372c5219020
     FS:  0000000000000000(0000) GS:ffff9372fbc00000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
     CR2: 00007f35bb7d5de0 CR3: 0000000020c2a006 CR4: 00000000001706f0
     DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
     DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
     Call Trace:
      <TASK>
      ? mark_held_locks+0x49/0x80
      ? lock_is_held_type+0xd7/0x130
      ? cma_cm_event_handler+0x49/0x200 [rdma_cm]
      cma_cm_event_handler+0x49/0x200 [rdma_cm]
      addr_handler+0xf1/0x1e0 [rdma_cm]
      ? lock_acquire+0xca/0x2f0
      ? lock_acquire+0xda/0x2f0
      process_one_req+0x43/0x170 [ib_core]
      process_one_work+0x274/0x590
      worker_thread+0x4f/0x3d0
      ? __pfx_worker_thread+0x10/0x10
      kthread+0xe7/0x110
      ? __pfx_kthread+0x10/0x10
      ret_from_fork+0x2c/0x50
      </TASK>
     irq event stamp: 1432669
     hardirqs last  enabled at (1432683): [<ffffffffac508eb2>] __up_console_sem+0x52/0x60
     hardirqs last disabled at (1432698): [<ffffffffac508e97>] __up_console_sem+0x37/0x60
     softirqs last  enabled at (1432518): [<ffffffffac48c985>] __irq_exit_rcu+0xc5/0x120
     softirqs last disabled at (1432509): [<ffffffffac48c985>] __irq_exit_rcu+0xc5/0x120
     ---[ end trace 0000000000000000 ]---

Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
---
 drivers/infiniband/ulp/rtrs/rtrs-clt.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
index 4c8f42e46e2f..760a7eb51297 100644
--- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
+++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
@@ -2074,6 +2074,7 @@ static int create_cm(struct rtrs_clt_con *con)
 		rtrs_err(s, "Failed to resolve address, err: %d\n", err);
 		goto destroy_cm;
 	}
+again:
 	/*
 	 * Combine connection status and session events. This is needed
 	 * for waiting two possible cases: cm_err has something meaningful
@@ -2083,10 +2084,15 @@ static int create_cm(struct rtrs_clt_con *con)
 			clt_path->state_wq,
 			con->cm_err || clt_path->state != RTRS_CLT_CONNECTING,
 			msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));
-	if (err == 0 || err == -ERESTARTSYS) {
-		if (err == 0)
-			err = -ETIMEDOUT;
-		/* Timedout or interrupted */
+	if (err == -ERESTARTSYS) {
+		/* interrupted,
+		 * try again to avoid the in-flight rtrs_clt_rdma_cm_handler()
+		 * getting a use-after-free
+		 */
+		goto again;
+	} else if (err == 0) {
+		err = -ETIMEDOUT;
+		/* Timedout */
 		goto errr;
 	}
 	if (con->cm_err < 0) {
-- 
2.29.2