Re: [PATCH-v2 1/2] mpt3sas: Refcount sas_device objects and fix unsafe list usage

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Wed, 2015-09-09 at 19:59 +0530, Chaitra Basappa wrote:
> From: Sreekanth Reddy [mailto:sreekanth.reddy@avagotech.com]
> Sent: Tuesday, September 08, 2015 5:26 PM
> To: Nicholas A. Bellinger
> Cc: linux-scsi; linux-kernel; James Bottomley; Calvin Owens; Christoph
> Hellwig; MPT-FusionLinux.pdl; kernel-team; Nicholas Bellinger; Chaitra
> Basappa
> Subject: Re: [PATCH-v2 1/2] mpt3sas: Refcount sas_device objects and fix
> unsafe list usage
> 
> On Sun, Aug 30, 2015 at 1:24 PM, Nicholas A. Bellinger <nab@daterainc.com>
> wrote:
> > From: Nicholas Bellinger <nab@linux-iscsi.org>
> >
> > These objects can be referenced concurrently throughout the driver, we
> > need a way to make sure threads can't delete them out from under each
> > other. This patch adds the refcount, and refactors the code to use it.
> >
> > Additionally, we cannot iterate over the sas_device_list without
> > holding the lock, or we risk corrupting random memory if items are
> > added or deleted as we iterate. This patch refactors
> > _scsih_probe_sas() to use the sas_device_list in a safe way.
> >
> > This patch is a port of Calvin's PATCH-v4 for mpt2sas code, atop
> > mpt3sas changes in scsi.git/for-next.
> >
> > Cc: Calvin Owens <calvinowens@fb.com>
> > Cc: Christoph Hellwig <hch@infradead.org>
> > Cc: Sreekanth Reddy <sreekanth.reddy@avagotech.com>
> > Cc: MPT-FusionLinux.pdl <MPT-FusionLinux.pdl@avagotech.com>
> > Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> > ---
> >  drivers/scsi/mpt3sas/mpt3sas_base.h      |  25 +-
> >  drivers/scsi/mpt3sas/mpt3sas_scsih.c     | 479
> > +++++++++++++++++++++----------
> >  drivers/scsi/mpt3sas/mpt3sas_transport.c |  18 +-
> >  3 files changed, 364 insertions(+), 158 deletions(-)
> >
> > @@ -2763,7 +2874,7 @@ _scsih_block_io_device(struct MPT3SAS_ADAPTER *ioc,
> > u16 handle)
> >         struct scsi_device *sdev;
> >         struct _sas_device *sas_device;
> >
> 
> [Sreekanth] Here sas_device_lock spin lock needs to be acquired before
> calling
>                   __mpt3sas_get_sdev_by_addr() function.
> 
> [Chaitra]Here instead of calling " __mpt3sas_get_sdev_by_handle()" function
> calling
> 	"mpt3sas_get_sdev_by_handle()" function will fixes "invalid page access"
> type of kernel panic
> 
> > -       sas_device = _scsih_sas_device_find_by_handle(ioc, handle);
> > +       sas_device = __mpt3sas_get_sdev_by_handle(ioc, handle);
> >         if (!sas_device)
> >                 return;
> >

Whoops, missed this comment in _scsih_block_io_device() from Sreekanth's
earlier reply.

Here's the updated incremental patch atop target-pending/for-next-merge
to use the protected callers for both cases.

Please review + ACK ASAP.

Thank you,

--nab

>From 8edb1554f7c2eb73cf70c9856aec01e786b9bcf9 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Tue, 8 Sep 2015 23:05:49 -0700
Subject: [PATCH] mpt3sas: Fix unprotected list lookup in v4.3-rc0 changes

This patch adds the missing mpt3sas_get_sdev_by_addr() protected
lookup usage in mpt3sas_transport_port_add() to avoid a NULL pointer
dereference when &ioc->sas_device_list or &ioc->sas_device_init_list
changes from below without a proper sas_device_get(sas_device)
reference held.

Also, use the protected mpt3sas_get_sdev_by_handle() lookup within
_scsih_block_io_device() as well.

Reported-by: Sreekanth Reddy <sreekanth.reddy@avagotech.com>
Reported-by: Chaitra Basappa <chaitra.basappa@avagotech.com>
Cc: Calvin Owens <calvinowens@fb.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c     | 2 +-
 drivers/scsi/mpt3sas/mpt3sas_transport.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index 0431cd0..9e68432 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -2933,7 +2933,7 @@ _scsih_block_io_device(struct MPT3SAS_ADAPTER *ioc, u16 handle)
 	struct scsi_device *sdev;
 	struct _sas_device *sas_device;
 
-	sas_device = __mpt3sas_get_sdev_by_handle(ioc, handle);
+	sas_device = mpt3sas_get_sdev_by_handle(ioc, handle);
 	if (!sas_device)
 		return;
 
diff --git a/drivers/scsi/mpt3sas/mpt3sas_transport.c b/drivers/scsi/mpt3sas/mpt3sas_transport.c
index 6074b11..ca36d7e 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_transport.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_transport.c
@@ -734,7 +734,7 @@ mpt3sas_transport_port_add(struct MPT3SAS_ADAPTER *ioc, u16 handle,
 	rphy->identify = mpt3sas_port->remote_identify;
 
 	if (mpt3sas_port->remote_identify.device_type == SAS_END_DEVICE) {
-		sas_device = __mpt3sas_get_sdev_by_addr(ioc,
+		sas_device = mpt3sas_get_sdev_by_addr(ioc,
 				    mpt3sas_port->remote_identify.sas_address);
 		if (!sas_device) {
 			dfailprintk(ioc, printk(MPT3SAS_FMT
-- 
1.9.1