Re: [PATCH] mpt2sas: mpt3sas: Fix memory corruption during initialization

From: Calvin Owens
Date: Wed May 06 2015 - 14:49:51 EST

On Monday 05/04 at 20:35 +0530, Sreekanth Reddy wrote:
> I have applied this patch on the latest upstream mpt3sas driver, then
> I have compiled and loaded the driver. In the driver logs I didn't
> see any attached drives are added to the OS, 'fdisk -l' command also
> doesn't list the drives which are actually attached to the HBA.
>
> When I debug this issue then I see that in '_scsih_target_alloc'
> driver is searching for sas_device from the lists
> 'sas_device_init_list' & 'sas_device_list' based on the device sas
> address using the function
> mpt3sas_scsih_sas_device_find_by_sas_address(), since this device is
> not in the 'sas_device_init_list' (as it is moved it to head list)
> driver exit from this function without updating the required device
> addition information.

Yes, I misunderstood that the initialization depended on the devices
still being on the init_list.

What's interesting about this is that when I tested it, it still worked.
I think the MPT2SAS_PORT_ENABLE_COMPLETE fw_event might zero
ioc->start_scan and allow scsih_scan_finished() to start probing devices
before all the devices are actually on the init_list. It seems to be
very repeatable per-machine whether or not it works.

But in any case, my patch was wrong.

> To solve the original problem (i.e memory corruption), here I have
> attached the patch, in this patch I have added one atomic flag
> is_on_sas_device_init_list in _sas_device_structure and I followed
> below algorithm.

The problem is that this only solves a single case. There isn't anything
to enforce that this or a similar chain of events can't happen elsewhere
in the code.

I think the best general solution would be to add a refcount to these
objects. They sit on a list that can be concurrently accessed from
multiple threads, so I think a refcount is the best way to ensure that
objects aren't freed out from under other users.

I'm working on a patchset that does this. I'm starting by adding a
refcount to the sas_device object only, and refactoring the code in
mpt2sas_scsih.c to use it. I should be able to send up a first version
of that pretty soon to get some feedback.

Thanks,
Calvin


> 1. when ever a device is added to sas_device_init_list then driver
> will set this atomic flag of this device to one.
>
> 2. And during the addition of this device to SCSI mid layer, if the
> device is successfully added to the OS then driver will move this
> device list in to sas_device_list list from sas_device_init_list list
> and at this time driver will reset this flag to zero. if device is
> failed to register with SCSI mid layer then also driver will reset
> this flag to zero in function _scsih_sas_device_remove and will remove
> the device entry from sas_device_init_list and will free the device
> structure.
>
> 3. Now when a device is removed then driver will receive target not responding event and in the function _scsih_device_remove_by_handle,
> a. driver will check whether addition of discovered devices to SML process is currently running or not,
> i. if addition (or registration) of discovered devices to SML process is running then driver will check whether device is in sas_device_init_list or not (by reading the atomic flag)?.
> if it is in a sas_device_init_list then driver will ignore this device removal event (since device registration with SML will fail and it is removed in function _scsih_sas_device_remove as mentioned in step 2).
> ii. if the device is not in a sas_device_init_list or addition (or registration) of discovered devices to SML process is already completed then device structure is removed from this function and this device entry is removed from sas_device_list.
>
> 4. if the device removal event is received after device structure is freed due to failure of device registration with SML them in the function _scsih_device_remove_by_handle driver won't find this device in the sas_device_list or in a sas_device_init_list and so driver will ignore this device removal event.
>
> Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@xxxxxxxxxxxxx>
> ---
> drivers/scsi/mpt2sas/mpt2sas_base.h | 2 ++
> drivers/scsi/mpt2sas/mpt2sas_scsih.c | 45 +++++++++++++++++++++++++++---------
> drivers/scsi/mpt3sas/mpt3sas_base.h | 2 ++
> drivers/scsi/mpt3sas/mpt3sas_scsih.c | 43 ++++++++++++++++++++++++++--------
> 4 files changed, 71 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.h b/drivers/scsi/mpt2sas/mpt2sas_base.h
> index caff8d1..1aa10d2 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_base.h
> +++ b/drivers/scsi/mpt2sas/mpt2sas_base.h
> @@ -376,6 +376,7 @@ struct _sas_device {
> u8 phy;
> u8 responding;
> u8 pfa_led_on;
> + atomic_t is_on_sas_device_init_list;
> };
>
> /**
> @@ -833,6 +834,7 @@ struct MPT2SAS_ADAPTER {
> u8 broadcast_aen_busy;
> u16 broadcast_aen_pending;
> u8 shost_recovery;
> + u8 discovered_device_addition_on;
>
> struct mutex reset_in_progress_mutex;
> spinlock_t ioc_reset_in_progress_lock;
> diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> index 3f26147..2a61286 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> +++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> @@ -590,13 +590,20 @@ _scsih_sas_device_remove(struct MPT2SAS_ADAPTER *ioc,
> struct _sas_device *sas_device)
> {
> unsigned long flags;
> + struct _sas_device *same_sas_device;
>
> if (!sas_device)
> return;
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + same_sas_device = _scsih_sas_device_find_by_handle(ioc,
> + sas_device->handle);
> + if (same_sas_device) {
> + list_del(&same_sas_device->list);
> + if (atomic_read(&sas_device->is_on_sas_device_init_list))
> + atomic_set(&sas_device->is_on_sas_device_init_list, 0);
> + kfree(same_sas_device);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> }
>
> @@ -658,6 +664,7 @@ _scsih_sas_device_init_add(struct MPT2SAS_ADAPTER *ioc,
> "(0x%04x), sas_addr(0x%016llx)\n", ioc->name, __func__,
> sas_device->handle, (unsigned long long)sas_device->sas_address));
>
> + atomic_set(&sas_device->is_on_sas_device_init_list, 1);
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> list_add_tail(&sas_device->list, &ioc->sas_device_init_list);
> _scsih_determine_boot_device(ioc, sas_device, 0);
> @@ -5364,8 +5371,14 @@ _scsih_device_remove_by_handle(struct MPT2SAS_ADAPTER *ioc, u16 handle)
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> sas_device = _scsih_sas_device_find_by_handle(ioc, handle);
> - if (sas_device)
> - list_del(&sas_device->list);
> + if (sas_device) {
> + if (ioc->discovered_device_addition_on &&
> + atomic_read(&sas_device->is_on_sas_device_init_list)) {
> + spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> + return;
> + } else
> + list_del(&sas_device->list);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> if (sas_device)
> _scsih_remove_device(ioc, sas_device);
> @@ -5391,8 +5404,14 @@ mpt2sas_device_remove_by_sas_address(struct MPT2SAS_ADAPTER *ioc,
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> sas_device = mpt2sas_scsih_sas_device_find_by_sas_address(ioc,
> sas_address);
> - if (sas_device)
> - list_del(&sas_device->list);
> + if (sas_device) {
> + if (ioc->discovered_device_addition_on &&
> + atomic_read(&sas_device->is_on_sas_device_init_list)) {
> + spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> + return;
> + } else
> + list_del(&sas_device->list);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> if (sas_device)
> _scsih_remove_device(ioc, sas_device);
> @@ -7978,32 +7997,36 @@ _scsih_probe_sas(struct MPT2SAS_ADAPTER *ioc)
> struct _sas_device *sas_device, *next;
> unsigned long flags;
>
> + ioc->discovered_device_addition_on = 1;
> /* SAS Device List */
> list_for_each_entry_safe(sas_device, next, &ioc->sas_device_init_list,
> list) {
>
> if (ioc->hide_drives)
> continue;
> -
> +
> if (!mpt2sas_transport_port_add(ioc, sas_device->handle,
> sas_device->sas_address_parent)) {
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + mpt2sas_transport_port_remove(ioc,
> + sas_device->sas_address,
> + sas_device->sas_address_parent);
> + _scsih_sas_device_remove(ioc, sas_device);
> continue;
> } else if (!sas_device->starget) {
> if (!ioc->is_driver_loading) {
> mpt2sas_transport_port_remove(ioc,
> sas_device->sas_address,
> sas_device->sas_address_parent);
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + _scsih_sas_device_remove(ioc, sas_device);
> continue;
> }
> }
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> list_move_tail(&sas_device->list, &ioc->sas_device_list);
> + atomic_dec(&sas_device->is_on_sas_device_init_list);
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> }
> + ioc->discovered_device_addition_on = 0;
> }
>
> /**
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.h b/drivers/scsi/mpt3sas/mpt3sas_base.h
> index afa8816..6188490 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_base.h
> +++ b/drivers/scsi/mpt3sas/mpt3sas_base.h
> @@ -315,6 +315,7 @@ struct _sas_device {
> u8 responding;
> u8 fast_path;
> u8 pfa_led_on;
> + atomic_t is_on_sas_device_init_list;
> };
>
> /**
> @@ -766,6 +767,7 @@ struct MPT3SAS_ADAPTER {
> u8 broadcast_aen_busy;
> u16 broadcast_aen_pending;
> u8 shost_recovery;
> + u8 discovered_device_addition_on;
>
> struct mutex reset_in_progress_mutex;
> spinlock_t ioc_reset_in_progress_lock;
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> index 5a97e32..53cc9ea 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> @@ -582,13 +582,20 @@ _scsih_sas_device_remove(struct MPT3SAS_ADAPTER *ioc,
> struct _sas_device *sas_device)
> {
> unsigned long flags;
> + struct _sas_device *same_sas_device;
>
> if (!sas_device)
> return;
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + same_sas_device = _scsih_sas_device_find_by_handle(ioc,
> + sas_device->handle);
> + if (same_sas_device) {
> + list_del(&same_sas_device->list);
> + if (atomic_read(&sas_device->is_on_sas_device_init_list))
> + atomic_set(&sas_device->is_on_sas_device_init_list, 0);
> + kfree(same_sas_device);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> }
>
> @@ -610,8 +616,14 @@ _scsih_device_remove_by_handle(struct MPT3SAS_ADAPTER *ioc, u16 handle)
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> sas_device = _scsih_sas_device_find_by_handle(ioc, handle);
> - if (sas_device)
> - list_del(&sas_device->list);
> + if (sas_device) {
> + if (ioc->discovered_device_addition_on &&
> + atomic_read(&sas_device->is_on_sas_device_init_list)) {
> + spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> + return;
> + } else
> + list_del(&sas_device->list);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> if (sas_device)
> _scsih_remove_device(ioc, sas_device);
> @@ -637,8 +649,14 @@ mpt3sas_device_remove_by_sas_address(struct MPT3SAS_ADAPTER *ioc,
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> sas_device = mpt3sas_scsih_sas_device_find_by_sas_address(ioc,
> sas_address);
> - if (sas_device)
> - list_del(&sas_device->list);
> + if (sas_device) {
> + if (ioc->discovered_device_addition_on &&
> + atomic_read(&sas_device->is_on_sas_device_init_list)) {
> + spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> + return;
> + } else
> + list_del(&sas_device->list);
> + }
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> if (sas_device)
> _scsih_remove_device(ioc, sas_device);
> @@ -663,6 +681,7 @@ _scsih_sas_device_add(struct MPT3SAS_ADAPTER *ioc,
> ioc->name, __func__, sas_device->handle,
> (unsigned long long)sas_device->sas_address));
>
> + atomic_set(&sas_device->is_on_sas_device_init_list, 1);
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> list_add_tail(&sas_device->list, &ioc->sas_device_list);
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> @@ -7610,14 +7629,17 @@ _scsih_probe_sas(struct MPT3SAS_ADAPTER *ioc)
> struct _sas_device *sas_device, *next;
> unsigned long flags;
>
> + ioc->discovered_device_addition_on = 1;
> /* SAS Device List */
> list_for_each_entry_safe(sas_device, next, &ioc->sas_device_init_list,
> list) {
>
> if (!mpt3sas_transport_port_add(ioc, sas_device->handle,
> sas_device->sas_address_parent)) {
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + mpt3sas_transport_port_remove(ioc,
> + sas_device->sas_address,
> + sas_device->sas_address_parent);
> + _scsih_sas_device_remove(ioc, sas_device);
> continue;
> } else if (!sas_device->starget) {
> /*
> @@ -7630,16 +7652,17 @@ _scsih_probe_sas(struct MPT3SAS_ADAPTER *ioc)
> mpt3sas_transport_port_remove(ioc,
> sas_device->sas_address,
> sas_device->sas_address_parent);
> - list_del(&sas_device->list);
> - kfree(sas_device);
> + _scsih_sas_device_remove(ioc, sas_device);
> continue;
> }
> }
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> list_move_tail(&sas_device->list, &ioc->sas_device_list);
> + atomic_dec(&sas_device->is_on_sas_device_init_list);
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> }
> + ioc->discovered_device_addition_on = 0;
> }
>
> /**
> --
> 2.0.2
>
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