linux-kernel - [PATCH] hpsa: fix NULL dereference in hpsa_put_ctlr_into_performant

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Date:	Mon, 14 Apr 2014 14:01:09 -0500
From:	scameron@...rdog.cce.hp.com
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Davidlohr Bueso <davidlohr@...com>,
	Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-pci@...r.kernel.org,
	Joerg Roedel <joro@...tes.org>,
	iommu@...ts.linux-foundation.org,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	scameron@...rdog.cce.hp.com
Subject: [PATCH] hpsa: fix NULL dereference in hpsa_put_ctlr_into_performant_mode()

Initialize local variable trans_support before it is used rather
than after.  It is supposed to contain the value of a register on the
controller containing bits that describe which transport modes the
controller supports (e.g. "performant", "ioaccel1",  "ioaccel2").  A
NULL pointer dereference will almost certainly occur if trans_support
is not initialized at the right point.  If for example the uninitialized
trans_support value does not have the bit set for ioaccel2 support when it
should be, then ioaccel2_alloc_cmds_and_bft() will not get called as it
should be and the h->ioaccel2_blockFetchTable array will remain NULL
instead of being allocated.  Too late, trans_support finally gets
initialized with the correct value with ioaccel2 mode bit set,
which later causes calc_bucket_map() to be called to fill in
h->ioaccel2_blockFetchTable[].  However h->ioaccel2_blockFetchTable
is NULL because it didn't get allocated because earlier trans_support
wasn't initialized at the right point.

Signed-off-by: Stephen M. Cameron <scameron@...rdog.cce.hp.com>
---
 drivers/scsi/hpsa.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 8cf4a0c..9a6e4a2 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -7463,6 +7463,10 @@ static void hpsa_put_ctlr_into_performant_mode(struct ctlr_info *h)
 	if (hpsa_simple_mode)
 		return;

+	trans_support = readl(&(h->cfgtable->TransportSupport));
+	if (!(trans_support & PERFORMANT_MODE))
+		return;
+
 	/* Check for I/O accelerator mode support */
 	if (trans_support & CFGTBL_Trans_io_accel1) {
 		transMethod |= CFGTBL_Trans_io_accel1 |
@@ -7479,10 +7483,6 @@ static void hpsa_put_ctlr_into_performant_mode(struct ctlr_info *h)
 	}

 	/* TODO, check that this next line h->nreply_queues is correct */
-	trans_support = readl(&(h->cfgtable->TransportSupport));
-	if (!(trans_support & PERFORMANT_MODE))
-		return;
-
 	h->nreply_queues = h->msix_vector > 0 ? h->msix_vector : 1;
 	hpsa_get_max_perf_mode_cmds(h);
 	/* Performant mode ring buffer and supporting data structures */
-- 
1.7.1

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