[3.8.y.z extended stable] Patch "[SCSI] isci: correct erroneous for_each_isci_host macro" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    [SCSI] isci: correct erroneous for_each_isci_host macro

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.21.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d64867644763e6d1da7dc6f849708bbfb5ffa394 Mon Sep 17 00:00:00 2001
From: Lukasz Dorau <lukasz.dorau at intel.com>
Date: Thu, 6 Feb 2014 12:23:20 -0800
Subject: [SCSI] isci: correct erroneous for_each_isci_host macro

commit c59053a23d586675c25d789a7494adfdc02fba57 upstream.

In the first place, the loop 'for' in the macro 'for_each_isci_host'
(drivers/scsi/isci/host.h:314) is incorrect, because it accesses
the 3rd element of 2 element array. After the 2nd iteration it executes
the instruction:
        ihost = to_pci_info(pdev)->hosts[2]
(while the size of the 'hosts' array equals 2) and reads an
out of range element.

In the second place, this loop is incorrectly optimized by GCC v4.8
(see http://marc.info/?l=linux-kernel&m=138998871911336&w=2).
As a result, on platforms with two SCU controllers,
the loop is executed more times than it can be (for i=0,1 and 2).
It causes kernel panic during entering the S3 state
and the following oops after 'rmmod isci':

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8131360b>] __list_add+0x1b/0xc0
Oops: 0000 [#1] SMP
RIP: 0010:[<ffffffff8131360b>]  [<ffffffff8131360b>] __list_add+0x1b/0xc0
Call Trace:
  [<ffffffff81661b84>] __mutex_lock_slowpath+0x114/0x1b0
  [<ffffffff81661c3f>] mutex_lock+0x1f/0x30
  [<ffffffffa03e97cb>] sas_disable_events+0x1b/0x50 [libsas]
  [<ffffffffa03e9818>] sas_unregister_ha+0x18/0x60 [libsas]
  [<ffffffffa040316e>] isci_unregister+0x1e/0x40 [isci]
  [<ffffffffa0403efd>] isci_pci_remove+0x5d/0x100 [isci]
  [<ffffffff813391cb>] pci_device_remove+0x3b/0xb0
  [<ffffffff813fbf7f>] __device_release_driver+0x7f/0xf0
  [<ffffffff813fc8f8>] driver_detach+0xa8/0xb0
  [<ffffffff813fbb8b>] bus_remove_driver+0x9b/0x120
  [<ffffffff813fcf2c>] driver_unregister+0x2c/0x50
  [<ffffffff813381f3>] pci_unregister_driver+0x23/0x80
  [<ffffffffa04152f8>] isci_exit+0x10/0x1e [isci]
  [<ffffffff810d199b>] SyS_delete_module+0x16b/0x2d0
  [<ffffffff81012a21>] ? do_notify_resume+0x61/0xa0
  [<ffffffff8166ce29>] system_call_fastpath+0x16/0x1b

The loop has been corrected.
This patch fixes kernel panic during entering the S3 state
and the above oops.

Signed-off-by: Lukasz Dorau <lukasz.dorau at intel.com>
Reviewed-by: Maciej Patelczyk <maciej.patelczyk at intel.com>
Tested-by: Lukasz Dorau <lukasz.dorau at intel.com>
Signed-off-by: Dan Williams <dan.j.williams at intel.com>
Signed-off-by: James Bottomley <JBottomley at Parallels.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/scsi/isci/host.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/isci/host.h b/drivers/scsi/isci/host.h
index 4911310..22a9bb1 100644
--- a/drivers/scsi/isci/host.h
+++ b/drivers/scsi/isci/host.h
@@ -311,9 +311,8 @@ static inline struct Scsi_Host *to_shost(struct isci_host *ihost)
 }

 #define for_each_isci_host(id, ihost, pdev) \
-	for (id = 0, ihost = to_pci_info(pdev)->hosts[id]; \
-	     id < ARRAY_SIZE(to_pci_info(pdev)->hosts) && ihost; \
-	     ihost = to_pci_info(pdev)->hosts[++id])
+	for (id = 0; id < SCI_MAX_CONTROLLERS && \
+	     (ihost = to_pci_info(pdev)->hosts[id]); id++)

 static inline void wait_for_start(struct isci_host *ihost)
 {
--
1.8.3.2