Re: Nokia N900: refcount_t underflow, use after free

[Suman Anna <s-anna@ti.com>]

On 03/09/2018 06:08 AM, Robin Murphy wrote:
> On 08/03/18 18:50, Pavel Machek wrote:
>> Hi!
>>
>>>> * Pavel Machek <pavel@ucw.cz> [180308 14:31]:
>>>>> Hi!
>>>>>
>>>>> I'm getting this warning... Has anyone seen/debugged that before?
>>>>> Unfortunately the backtrace does not seem to be too useful :-(.
>>>>
>>>> Adding Suman to Cc, as it points to arm_iommu_release_mapping().
>>>
>>> Hmm, we need to find out if the failure paths in isp_probe() are
>>> mismatched, or if this is coming from some mismatch between the OMAP
>>> IOMMU driver and the DMA plumbing. AFAIK, the cleanup paths in this
>>
>> Well, camera only started to work on N900 pretty recently. Let me add
>> some debug printks...
>>
>> Camera does not work in 4.16.0-rc4-next-20180308-dirty.
>>
>> I see this. It looks like problem in isp error paths, indeed:
> 
> Well, there certainly seems to be an obvious bug wherein
> isp_detach_iommu() just releases the mapping directly without calling
> arm_iommu_detach_device() to balance the equivalent attach. That can't
> be helping.

Indeed, I have been able to reproduce the same warning using a
standalone test module, and the missing arm_iommu_detach_device() is
causing the warning after probe (during failure path) or during remove.

regards
Suman

> 
> Robin.
> 
>>
>> [    1.672210] bus: 'platform': driver_probe_device: matched device
>> 480bc000.isp with dr
>> iver omap3isp
>> [    1.681976] isp_probe: 1
>> [    1.684906] isp_probe: 2
>> [    1.687591] isp_probe: 3
>> [    1.690338] isp_probe: 4
>> [    1.693054] omap3isp 480bc000.isp: 480bc000.isp supply vdd-csiphy1
>> not found, using d
>> ummy regulator
>> [    1.702728] omap3isp 480bc000.isp: 480bc000.isp supply vdd-csiphy2
>> not found, using d
>> ummy regulator
>> [    1.712402] isp_probe: 5
>> [    1.715393] omap3isp 480bc000.isp: Revision 2.0 found
>> [    1.720794] isp_probe: 6
>> [    1.723815] isp_probe: 7
>> [    1.726715] omap-iommu 480bd400.mmu: 480bd400.mmu: version 1.1
>> [    1.732849] isp_probe: 8
>> [    1.735656] isp_probe: 9
>> [    1.738403] isp_probe: 10
>> [    1.741241] isp_probe: f3
>> [    1.744018] iommu_release_mapping... ce4d9500 ce4d949c
>> [    1.749450] iommu_release_mapping... ok
>> [    1.753479] isp_probe: f4
>> [    1.756286] clk_unregister: unregistering prepared clock: cam_xclka
>> [    1.762878] clk_unregister: unregistering prepared clock: cam_xclkb
>> [    1.769500] isp_probe: f5
>> [    1.772430] iommu_release_mapping... ce4d9500 ce4d949c
>> [    1.777862] ------------[ cut here ]------------
>> [    1.782745] WARNING: CPU: 0 PID: 1 at lib/refcount.c:187
>> refcount_sub_and_test+0x94/0
>> xa8
>> [    1.791290] refcount_t: underflow; use-after-free.
>> [    1.796356] Modules linked in:
>> [    1.799591] CPU: 0 PID: 1 Comm: swapper Not tainted
>> 4.16.0-rc4-next-20180308-dirty #7
>> 3
>> [    1.807922] Hardware name: Nokia RX-51 board
>> [    1.812469] [<c010d6cc>] (unwind_backtrace) from [<c010b568>]
>> (show_stack+0x10/0x14)
>> [    1.820648] [<c010b568>] (show_stack) from [<c0127df4>]
>> (__warn+0xe8/0x110)
>> ...
>> [    1.968688] iommu_release_mapping... ok
>> [    1.973754] bus: 'platform': driver_probe_device: matched device
>> n900-battery with driver rx51-battery
>> [    1.984436] bus: 'platform': driver_probe_device: matched device
>> 48002524.bandgap with driver ti-soc-thermal
>>
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index 8c398fe..16f4c69 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -2251,8 +2251,11 @@ static int extend_iommu_mapping(struct
>> dma_iommu_mapping *mapping)
>>     void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping)
>>   {
>> +    printk("iommu_release_mapping... %lx %lx\n", mapping,
>> mapping->domain);
>>       if (mapping)
>>           kref_put(&mapping->kref, release_iommu_mapping);
>> +    printk("iommu_release_mapping... ok\n");
>> +   
>>   }
>>   EXPORT_SYMBOL_GPL(arm_iommu_release_mapping);
>>   diff --git a/drivers/media/platform/omap3isp/isp.c
>> b/drivers/media/platform/omap3isp/isp.c
>> index 8eb000e..4d58683 100644
>> --- a/drivers/media/platform/omap3isp/isp.c
>> +++ b/drivers/media/platform/omap3isp/isp.c
>> @@ -2193,12 +2193,14 @@ static int isp_probe(struct platform_device
>> *pdev)
>>       int ret;
>>       int i, m;
>>   +    printk("isp_probe: 1\n");
>>       isp = devm_kzalloc(&pdev->dev, sizeof(*isp), GFP_KERNEL);
>>       if (!isp) {
>>           dev_err(&pdev->dev, "could not allocate memory\n");
>>           return -ENOMEM;
>>       }
>>   +        printk("isp_probe: 2\n");
>>       ret = fwnode_property_read_u32(of_fwnode_handle(pdev->dev.of_node),
>>                          "ti,phy-type", &isp->phy_type);
>>       if (ret)
>> @@ -2219,6 +2221,8 @@ static int isp_probe(struct platform_device *pdev)
>>       mutex_init(&isp->isp_mutex);
>>       spin_lock_init(&isp->stat_lock);
>>   +            printk("isp_probe: 3\n");
>> +
>>       ret = v4l2_async_notifier_parse_fwnode_endpoints(
>>           &pdev->dev, &isp->notifier, sizeof(struct isp_async_subdev),
>>           isp_fwnode_parse);
>> @@ -2232,6 +2236,7 @@ static int isp_probe(struct platform_device *pdev)
>>       if (ret)
>>           goto error;
>>   +                printk("isp_probe: 4\n");
>>       platform_set_drvdata(pdev, isp);
>>         /* Regulators */
>> @@ -2258,6 +2263,7 @@ static int isp_probe(struct platform_device *pdev)
>>               return PTR_ERR(isp->mmio_base[map_idx]);
>>       }
>>   +    printk("isp_probe: 5\n");
>>       ret = isp_get_clocks(isp);
>>       if (ret < 0)
>>           goto error;
>> @@ -2277,6 +2283,7 @@ static int isp_probe(struct platform_device *pdev)
>>           goto error;
>>       }
>>   +        printk("isp_probe: 6\n");
>>       ret = isp_reset(isp);
>>       if (ret < 0)
>>           goto error_isp;
>> @@ -2306,6 +2313,7 @@ static int isp_probe(struct platform_device *pdev)
>>               isp->mmio_base[OMAP3_ISP_IOMEM_CSI2A_REGS1]
>>               + isp_res_maps[m].offset[i];
>>   +        printk("isp_probe: 7\n");
>>       isp->mmio_hist_base_phys =
>>           mem->start + isp_res_maps[m].offset[OMAP3_ISP_IOMEM_HIST];
>>   @@ -2316,6 +2324,8 @@ static int isp_probe(struct platform_device
>> *pdev)
>>           goto error_isp;
>>       }
>>   +        printk("isp_probe: 8\n");
>> +
>>       /* Interrupt */
>>       ret = platform_get_irq(pdev, 0);
>>       if (ret <= 0) {
>> @@ -2325,6 +2335,7 @@ static int isp_probe(struct platform_device *pdev)
>>       }
>>       isp->irq_num = ret;
>>   +            printk("isp_probe: 9\n");
>>       if (devm_request_irq(isp->dev, isp->irq_num, isp_isr, IRQF_SHARED,
>>                    "OMAP3 ISP", isp)) {
>>           dev_err(isp->dev, "Unable to request IRQ\n");
>> @@ -2332,6 +2343,7 @@ static int isp_probe(struct platform_device *pdev)
>>           goto error_iommu;
>>       }
>>   +                printk("isp_probe: 10\n");
>>       /* Entities */
>>       ret = isp_initialize_modules(isp);
>>       if (ret < 0)
>> @@ -2345,27 +2357,35 @@ static int isp_probe(struct platform_device
>> *pdev)
>>       if (ret < 0)
>>           goto error_register_entities;
>>   +                    printk("isp_probe: 11\n");
>>       isp->notifier.ops = &isp_subdev_notifier_ops;
>>         ret = v4l2_async_notifier_register(&isp->v4l2_dev,
>> &isp->notifier);
>>       if (ret)
>>           goto error_register_entities;
>>   +                    printk("isp_probe: 12\n");   
>>       isp_core_init(isp, 1);
>> +                    printk("isp_probe: 13\n");       
>>       omap3isp_put(isp);
>>         return 0;
>>     error_register_entities:
>> +                    printk("isp_probe: f1\n");       
>>       isp_unregister_entities(isp);
>>   error_modules:
>> +                        printk("isp_probe: f2\n");       
>>       isp_cleanup_modules(isp);
>>   error_iommu:
>> +                            printk("isp_probe: f3\n");       
>>       isp_detach_iommu(isp);
>>   error_isp:
>> +                            printk("isp_probe: f4\n");       
>>       isp_xclk_cleanup(isp);
>>       __omap3isp_put(isp, false);
>>   error:
>> +                        printk("isp_probe: f5\n");           
>>       v4l2_async_notifier_cleanup(&isp->notifier);
>>       mutex_destroy(&isp->isp_mutex);
>>  
>>
>>
>>
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