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Subject[PATCH 4.4 50/96] IB/srp: Avoid that a cable pull can trigger a kernel crash
Date
4.4-stable 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/ulp/srp/ib_srp.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)

--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -670,12 +670,19 @@ static void srp_path_rec_completion(int
static int srp_lookup_path(struct srp_rdma_ch *ch)
{
struct srp_target_port *target = ch->target;
- int ret;
+ int ret = -ENODEV;

ch->path.numb_path = 1;

init_completion(&ch->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;
+
ch->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
target->srp_host->srp_dev->dev,
target->srp_host->port,
@@ -689,18 +696,24 @@ static int srp_lookup_path(struct srp_rd
GFP_KERNEL,
srp_path_rec_completion,
ch, &ch->path_query);
- if (ch->path_query_id < 0)
- return ch->path_query_id;
+ ret = ch->path_query_id;
+ if (ret < 0)
+ goto put;

ret = wait_for_completion_interruptible(&ch->done);
if (ret < 0)
- return ret;
+ goto put;

- if (ch->status < 0)
+ ret = ch->status;
+ if (ret < 0)
shost_printk(KERN_WARNING, target->scsi_host,
PFX "Path record query failed\n");

- return ch->status;
+put:
+ scsi_host_put(target->scsi_host);
+
+out:
+ return ret;
}

static int srp_send_req(struct srp_rdma_ch *ch, bool multich)

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