On 07/14/2015 01:23 PM, Nagarajkumar Narayanan wrote:
>
> Patch Description:
>
> In mpt2sas driver due to lack of synchronization between ioctl,
> BRM status access through sysfs, pci resource removal kernel oops
> happen as ioctl path and BRM status sysfs access path still tries
> to access the removed resources
>
> kernel: BUG: unable to handle kernel paging request at ffffc900171e0000
>
> Oops: 0000 [#1] SMP
>
> Two locks added to provide syncrhonization
>
> 1. pci_access_mutex: Mutex to synchronize ioctl,sysfs show path and
> pci resource handling. PCI resource freeing will lead to free
> vital hardware/memory resource, which might be in use by cli/sysfs
> path functions resulting in Null pointer reference followed by kernel
> crash. To avoid the above race condition we use mutex syncrhonization
> which ensures the syncrhonization between cli/sysfs_show path
>
> 2. spinlock on list operations over IOCs
>
> Case: when multiple warpdrive cards(IOCs) are in use
> Each IOC will added to the ioc list stucture on initialization.
> Watchdog threads run at regular intervals to check IOC for any
> fault conditions which will trigger the dead_ioc thread to
> deallocate pci resource, resulting deleting the IOC netry from list,
> this deletion need to protected by spinlock to enusre that
> ioc removal is syncrhonized, if not synchronized it might lead to
> list_del corruption as the ioc list is traversed in cli path
>
>
> From 8db4d8194276ba420a4e93de4b09df6da5a934e4 Mon Sep 17 00:00:00 2001
> From: Nagarajkumar Narayanan <nagarajkumar.narayanan@xxxxxxxxxxx>
> Date: Tue, 14 Jul 2015 16:33:56 +0530
> Subject: [PATCH] mpt2sas setpci reset oops fix
>
> setpci reset on nytro warpdrive card along with sysfs access and
> cli ioctl access resulted in kernel oops
>
> 1. pci_access_mutex lock added to provide synchronization between IOCTL,
> sysfs, PCI resource handling path
>
> 2. gioc_lock spinlock to protect list operations over multiple
> controllers
>
> Signed-off-by: Nagarajkumar Narayanan <nagarajkumar.narayanan@xxxxxxxxxxx>
> ---
> * v2
> - removed is_warpdrive condition for pci_access_mutex lock
>
> * v1
> - using DEFINE_SPINLOCK() to initialize the lock at compile time instead
> of using spin_lock_init
>
> drivers/scsi/mpt2sas/mpt2sas_base.c | 7 +++++++
> drivers/scsi/mpt2sas/mpt2sas_base.h | 19 ++++++++++++++++++-
> drivers/scsi/mpt2sas/mpt2sas_ctl.c | 33 +++++++++++++++++++++++++++++----
> drivers/scsi/mpt2sas/mpt2sas_scsih.c | 15 ++++++++++++++-
> 4 files changed, 68 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
> index 11248de..f04dcc0 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_base.c
> +++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
> @@ -108,13 +108,17 @@ _scsih_set_fwfault_debug(const char *val, struct kernel_param *kp)
> {
> int ret = param_set_int(val, kp);
> struct MPT2SAS_ADAPTER *ioc;
> + unsigned long flags;
>
> if (ret)
> return ret;
>
> + /* global ioc spinlock to protect controller list on list operations */
> printk(KERN_INFO "setting fwfault_debug(%d)\n", mpt2sas_fwfault_debug);
> + spin_lock_irqsave(&gioc_lock, flags);
> list_for_each_entry(ioc, &mpt2sas_ioc_list, list)
> ioc->fwfault_debug = mpt2sas_fwfault_debug;
> + spin_unlock_irqrestore(&gioc_lock, flags);
> return 0;
> }
>
> @@ -4436,6 +4440,8 @@ mpt2sas_base_free_resources(struct MPT2SAS_ADAPTER *ioc)
> __func__));
>
> if (ioc->chip_phys && ioc->chip) {
> + /* synchronizing freeing resource with pci_access_mutex lock */
> + mutex_lock(&ioc->pci_access_mutex);
> _base_mask_interrupts(ioc);
> ioc->shost_recovery = 1;
> _base_make_ioc_ready(ioc, CAN_SLEEP, SOFT_RESET);
> @@ -4454,6 +4460,7 @@ mpt2sas_base_free_resources(struct MPT2SAS_ADAPTER *ioc)
> pci_disable_pcie_error_reporting(pdev);
> pci_disable_device(pdev);
> }
> + mutex_unlock(&ioc->pci_access_mutex);
> return;
> }
>
Lock imbalance. Please move the call to 'mutex_lock()' out of the
'if' clause.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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