[PATCH 3/3] scsi: aacraid: Prevent crash in case of free interrupt during scsi EH path

["Guilherme G. Piccoli" <gpiccoli@linux.vnet.ibm.com>]

As part of the scsi EH path, aacraid performs a reinitialization of
the adapter, which encompass freeing resources and IRQs, NULLifying
lots of pointers, and then initialize it all over again.
We've identified a problem during the free IRQ portion of this path
if CONFIG_DEBUG_SHIRQ is enabled on kernel config file.

Happens that, in case this flag was set, right after free_irq()
effectively clears the interrupt, it checks if it was requested
as IRQF_SHARED. In positive case, it performs another call to the
IRQ handler on driver. Problem is: since aacraid currently free
some resources *before* freeing the IRQ, once free_irq() path
calls the handler again (due to CONFIG_DEBUG_SHIRQ), aacraid
crashes due to NULL pointer dereference with the following trace:

  aac_src_intr_message+0xf8/0x740 [aacraid]
  __free_irq+0x33c/0x4a0
  free_irq+0x78/0xb0
  aac_free_irq+0x13c/0x150 [aacraid]
  aac_reset_adapter+0x2e8/0x970 [aacraid]
  aac_eh_reset+0x3a8/0x5d0 [aacraid]
  scsi_try_host_reset+0x74/0x180
  scsi_eh_ready_devs+0xc70/0x1510
  scsi_error_handler+0x624/0xa20

This patch prevents the crash by changing the order of the
deinitialization in this path of aacraid: first we clear the IRQ,
then we free other resources. No functional change intended.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
---
 drivers/scsi/aacraid/commsup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c
index 2abe8fd83494..bec9f3193f60 100644
--- a/drivers/scsi/aacraid/commsup.c
+++ b/drivers/scsi/aacraid/commsup.c
@@ -1554,6 +1554,7 @@ static int _aac_reset_adapter(struct aac_dev *aac, int forced, u8 reset_type)
 	 * will ensure that i/o is queisced and the card is flushed in that
 	 * case.
 	 */
+	aac_free_irq(aac);
 	aac_fib_map_free(aac);
 	dma_free_coherent(&aac->pdev->dev, aac->comm_size, aac->comm_addr,
 			  aac->comm_phys);
@@ -1561,7 +1562,6 @@ static int _aac_reset_adapter(struct aac_dev *aac, int forced, u8 reset_type)
 	aac->comm_phys = 0;
 	kfree(aac->queues);
 	aac->queues = NULL;
-	aac_free_irq(aac);
 	kfree(aac->fsa_dev);
 	aac->fsa_dev = NULL;
 
-- 
2.15.0