linux-kernel - [PATCH AUTOSEL for 4.9 49/55] scsi: aacraid: Prevent crash in case of free interrupt during scsi EH path

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Date:   Wed, 24 Jan 2018 04:15:55 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     "Guilherme G. Piccoli" <gpiccoli@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 49/55] scsi: aacraid: Prevent crash in case of
 free interrupt during scsi EH path

From: "Guilherme G. Piccoli" <gpiccoli@...ux.vnet.ibm.com>

[ Upstream commit e4717292ddebcfe231651b5aff9fa19ca158d178 ]

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@...ux.vnet.ibm.com>
Reviewed-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@...rosemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.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 0aeecec1f5ea..e2962f15c189 100644
--- a/drivers/scsi/aacraid/commsup.c
+++ b/drivers/scsi/aacraid/commsup.c
@@ -1416,13 +1416,13 @@ static int _aac_reset_adapter(struct aac_dev *aac, int forced)
 	 * will ensure that i/o is queisced and the card is flushed in that
 	 * case.
 	 */
+	aac_free_irq(aac);
 	aac_fib_map_free(aac);
 	pci_free_consistent(aac->pdev, aac->comm_size, aac->comm_addr, aac->comm_phys);
 	aac->comm_addr = NULL;
 	aac->comm_phys = 0;
 	kfree(aac->queues);
 	aac->queues = NULL;
-	aac_free_irq(aac);
 	kfree(aac->fsa_dev);
 	aac->fsa_dev = NULL;
 	quirks = aac_get_driver_ident(index)->quirks;
-- 
2.11.0