Re: [PATCH] iommu/omap: Fix regression in probe for NULL pointer dereference

2022-03-31 Thread Drew Fustini 
On TLhu, Mar 31, 2022 at 09:23:01AM +0300, Tony Lindgren wrote:
> Commit 3f6634d997db ("iommu: Use right way to retrieve iommu_ops") started
> triggering a NULL pointer dereference for some omap variants:
> 
> __iommu_probe_device from probe_iommu_group+0x2c/0x38
> probe_iommu_group from bus_for_each_dev+0x74/0xbc
> bus_for_each_dev from bus_iommu_probe+0x34/0x2e8
> bus_iommu_probe from bus_set_iommu+0x80/0xc8
> bus_set_iommu from omap_iommu_init+0x88/0xcc
> omap_iommu_init from do_one_initcall+0x44/0x24
> 
> This is caused by omap iommu probe returning 0 instead of ERR_PTR(-ENODEV)
> as noted by Jason Gunthorpe .
> 
> Looks like the regression already happened with an earlier commit
> 6785eb9105e3 ("iommu/omap: Convert to probe/release_device() call-backs")
> that changed the function return type and missed converting one place.
> 
> Cc: Drew Fustini 
> Cc: Lu Baolu 
> Cc: Suman Anna 
> Suggested-by: Jason Gunthorpe 
> Fixes: 6785eb9105e3 ("iommu/omap: Convert to probe/release_device() 
> call-backs")
> Fixes: 3f6634d997db ("iommu: Use right way to retrieve iommu_ops")
> Signed-off-by: Tony Lindgren 
> ---
>  drivers/iommu/omap-iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
> --- a/drivers/iommu/omap-iommu.c
> +++ b/drivers/iommu/omap-iommu.c
> @@ -1661,7 +1661,7 @@ static struct iommu_device 
> *omap_iommu_probe_device(struct device *dev)
>   num_iommus = of_property_count_elems_of_size(dev->of_node, "iommus",
>sizeof(phandle));
>   if (num_iommus < 0)
> - return 0;
> + return ERR_PTR(-ENODEV);
>  
>   arch_data = kcalloc(num_iommus + 1, sizeof(*arch_data), GFP_KERNEL);
>   if (!arch_data)
> -- 
> 2.35.1

Mainline with omap2plus_defconfig now boots ok on my BeagleBoard-X15
with the TI AM5728 SoC after this patch is applied.

Tested-by: Drew Fustini 

thanks,
drew
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Re: [PATCH v4 8/9] iommu: Remove unused argument in is_attach_deferred

2022-03-31 Thread Drew Fustini 
On Wed, Mar 30, 2022 at 02:33:23PM -0300, Jason Gunthorpe wrote:
> On Wed, Mar 30, 2022 at 08:19:37PM +0300, Tony Lindgren wrote:
> 
> > > > __iommu_probe_device from probe_iommu_group+0x2c/0x38
> > > > probe_iommu_group from bus_for_each_dev+0x74/0xbc
> > > > bus_for_each_dev from bus_iommu_probe+0x34/0x2e8
> > > > bus_iommu_probe from bus_set_iommu+0x80/0xc8
> > > > bus_set_iommu from omap_iommu_init+0x88/0xcc
> > > > omap_iommu_init from do_one_initcall+0x44/0x24c
> > > > 
> > > > Any ideas for a fix?
> > > > 
> > > > It would be good to fix this quickly so we don't end up with a broken
> > > > v5.18-rc1..
> > > > 
> > > > For reference, this is mainline commit 41bb23e70b50 ("iommu: Remove 
> > > > unused
> > > > argument in is_attach_deferred").
> > > 
> > > Are you confident in the bisection? I don't see how that commit could
> > > NULL deref..
> > 
> > Oops sorry you're right, the breaking commit is a different patch, it's
> > 3f6634d997db ("iommu: Use right way to retrieve iommu_ops") instead. I must
> > have picked the wrong commit while testing.
> 
> That makes alot more sense
>  
> > > Can you find the code that is the NULL deref?
> > 
> > I can debug a bit more tomorrow.
> 
> Looks like omap's omap_iommu_probe_device() is buggy, it returns 0 on
> error paths:
> 
>   num_iommus = of_property_count_elems_of_size(dev->of_node, "iommus",
>sizeof(phandle));
>   if (num_iommus < 0)
>   return 0;
> 
> This function needs to return an errno -ENODEV
> 
> Otherwise it causes a NULL dev->iommu->iommu_dev and dev_iommu_ops() will
> crash.
> 
> Jason

I tried to boot current mainline (787af64d05cd) on am57xx-evm and it
failed to boot. I made the change you suggested and it boots okay now:
https://gist.github.com/pdp7/918eefe03b5c5db3b5d28d819f6a27f6

thanks,
drew

diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
index 4aab631ef517..d9cf2820c02e 100644
--- a/drivers/iommu/omap-iommu.c
+++ b/drivers/iommu/omap-iommu.c
@@ -1661,7 +1661,7 @@ static struct iommu_device 
*omap_iommu_probe_device(struct device *dev)
num_iommus = of_property_count_elems_of_size(dev->of_node, "iommus",
 sizeof(phandle));
if (num_iommus < 0)
-   return 0;
+   return ERR_PTR(-ENODEV);

arch_data = kcalloc(num_iommus + 1, sizeof(*arch_data), GFP_KERNEL);
if (!arch_data)

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