[PATCH v2] isci: correct erroneous for_each_isci_host macro

From: Lukasz Dorau
Date: Tue Jan 21 2014 - 06:34:02 EST

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@xxxxxxxxx>
Reviewed-by: Maciej Patelczyk <maciej.patelczyk@xxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Tested-by: Lukasz Dorau <lukasz.dorau@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
- updated changelog, removed initialization of ihost,
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)

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