linux-kernel - [PATCH 3.2 008/125] IB/srp: Fix a sporadic crash triggered by cable pulling

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Message-ID: <lsq.1404846110.291596992@decadent.org.uk>
Date:	Tue, 08 Jul 2014 20:01:50 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Roland Dreier" <roland@...estorage.com>,
	"Bart Van Assche" <bvanassche@....org>,
	"Sagi Grimberg" <sagig@...lanox.com>
Subject: [PATCH 3.2 008/125] IB/srp: Fix a sporadic crash triggered by
 cable pulling

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

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

From: Bart Van Assche <bvanassche@....org>

commit 024ca90151f5e4296d30f72c13ff9a075e23c9ec upstream.

Avoid that the loops that iterate over the request ring can encounter
a pointer to a SCSI command in req->scmnd that is no longer associated
with that request. If the function srp_unmap_data() is invoked twice
for a SCSI command that is not in flight then that would cause
ib_fmr_pool_unmap() to be invoked with an invalid pointer as argument,
resulting in a kernel oops.

Reported-by: Sagi Grimberg <sagig@...lanox.com>
Reference: http://thread.gmane.org/gmane.linux.drivers.rdma/19068/focus=19069
Signed-off-by: Bart Van Assche <bvanassche@....org>
Reviewed-by: Sagi Grimberg <sagig@...lanox.com>
Signed-off-by: Roland Dreier <roland@...estorage.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/ulp/srp/ib_srp.c | 6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1353,6 +1353,12 @@ err_unmap:
 err_iu:
 	srp_put_tx_iu(target, iu, SRP_IU_CMD);
 
+	/*
+	 * Avoid that the loops that iterate over the request ring can
+	 * encounter a dangling SCSI command pointer.
+	 */
+	req->scmnd = NULL;
+
 	spin_lock_irqsave(&target->lock, flags);
 	list_add(&req->list, &target->free_reqs);
 

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