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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Bart Van Assche" <bart.vanassche@wdc.com>,
        "Sagi Grimberg" <sagi@grimberg.me>,
        "Doug Ledford" <dledford@redhat.com>
Date:   Sun, 11 Feb 2018 04:20:06 +0000
Message-ID: <lsq.1518322806.325817887@decadent.org.uk>
Subject: [PATCH 3.2 10/79] IB/srp: Avoid that a cable pull can trigger a
 kernel crash
In-Reply-To: <lsq.1518322802.943358572@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.2.99-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bart.vanassche@wdc.com>

commit 8a0d18c62121d3c554a83eb96e2752861d84d937 upstream.

This patch fixes the following kernel crash:

general protection fault: 0000 [#1] PREEMPT SMP
Workqueue: ib_mad2 timeout_sends [ib_core]
Call Trace:
 ib_sa_path_rec_callback+0x1c4/0x1d0 [ib_core]
 send_handler+0xb2/0xd0 [ib_core]
 timeout_sends+0x14d/0x220 [ib_core]
 process_one_work+0x200/0x630
 worker_thread+0x4e/0x3b0
 kthread+0x113/0x150

Fixes: commit aef9ec39c47f ("IB: Add SCSI RDMA Protocol (SRP) initiator")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -310,10 +310,19 @@ static void srp_path_rec_completion(int
 
 static int srp_lookup_path(struct srp_target_port *target)
 {
+	int ret = -ENODEV;
+
 	target->path.numb_path = 1;
 
 	init_completion(&target->done);
 
+	/*
+	 * Avoid that the SCSI host can be removed by srp_remove_target()
+	 * before srp_path_rec_completion() is called.
+	 */
+	if (!scsi_host_get(target->scsi_host))
+		goto out;
+
 	target->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
 						   target->srp_host->srp_dev->dev,
 						   target->srp_host->port,
@@ -327,16 +336,22 @@ static int srp_lookup_path(struct srp_ta
 						   GFP_KERNEL,
 						   srp_path_rec_completion,
 						   target, &target->path_query);
-	if (target->path_query_id < 0)
-		return target->path_query_id;
+	ret = target->path_query_id;
+	if (ret < 0)
+		goto put;
 
 	wait_for_completion(&target->done);
 
-	if (target->status < 0)
+	ret = target->status;
+	if (ret < 0)
 		shost_printk(KERN_WARNING, target->scsi_host,
 			     PFX "Path record query failed\n");
 
-	return target->status;
+put:
+	scsi_host_put(target->scsi_host);
+
+out:
+	return ret;
 }
 
 static int srp_send_req(struct srp_target_port *target)