[SCSI] 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.

Fixes: e1f7de0cdd68d246d7008241cd9e443a54f880a8
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Reported-by: Baoquan He <bhe@redhat.com>
Tested-by: Baoquan He <bhe@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 8cf4a0c69baf4cebfc5ecb4fb28c029c4455d886..9a6e4a2cd072421df1980edfa4c8f914398b3991 100644 (file)
--- 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 */