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About the security content of iOS 15.4.1 and iPadOS 15.4.1

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Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#21

Earlier quoted context omitted.

Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension. Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse. But SiDeLoADiNg is what is threatening users’ security.

> Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension Why?

[deleted]

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#22

Earlier quoted context omitted.

It's a kext for decoding HEVC, H.264, and VP9.

Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension. Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse. But SiDeLoADiNg is what is threatening users’ security.

This is how macOS is designed. macOS has over 100 kexts in a fresh install (IIRC) to keep the main kernel as small and error-free as reasonably possible without being a full microkernel and taking the performance hit that causes. This makes it a Hybrid kernel, neither a full microkernel (safety at cost of performance) or monolithic kernel (performance at cost of safety).

Other hybrid kernels include Windows and BeOS, though on Windows the kernel/extension separation is less clearly defined.

https://en.wikipedia.org/wiki/Hybrid_kernel

> "Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse."

Heck... NO. Drivers are still in kernel space like ever. I don't know where you got that impression. Windows isn't a microkernel, it's got plenty of kernel drivers for everything. Only UMDF Drivers are userspace, and while there are many of them, none of them are as complex as a GPU. A GPU Driver in userspace on Windows would be massively performance bottlenecked. Microsoft even states in their documentation "File system drivers, display drivers (for full display devices, not display-only display devices), and print drivers cannot be UMDF drivers."

https://docs.microsoft.com/en-us/windows-hardware/drivers/wd...

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#23

Earlier quoted context omitted.

Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension. Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse. But SiDeLoADiNg is what is threatening users’ security.

This is how macOS is designed. macOS has over 100 kexts in a fresh install (IIRC) to keep the main kernel as small and error-free as reasonably possible without being a full microkernel and taking the performance hit that causes. This makes it a Hybrid kernel, neither a full microkernel (safety at cost of performance) or monolithic kernel (performance at cost of safety). Other hybrid kernels include Windows and BeOS,…

Yes, and display drivers are in large part in user mode too:

https://docs.microsoft.com/en-us/windows-hardware/drivers/di...

This has been the case since Windows Vista WDDM.

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#24

Earlier quoted context omitted.

Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension. Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse. But SiDeLoADiNg is what is threatening users’ security.

> Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension Why?

For exactly the reason they have to patch it. For exactly the same reason they are now disallowing custom kernel extensions. Apple engineers are not perfect machines, writing perfect code without issues. And so, here we are. Years in the wild exploit in a kernel extension for decoding h264. Ridiculous.

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#25

Earlier quoted context omitted.

This is how macOS is designed. macOS has over 100 kexts in a fresh install (IIRC) to keep the main kernel as small and error-free as reasonably possible without being a full microkernel and taking the performance hit that causes. This makes it a Hybrid kernel, neither a full microkernel (safety at cost of performance) or monolithic kernel (performance at cost of safety). Other hybrid kernels include Windows and BeOS,…

Yes, and display drivers are in large part in user mode too: https://docs.microsoft.com/en-us/windows-hardware/drivers/di... This has been the case since Windows Vista WDDM.

So they are on Linux, macOS and other platforms. In fact the DirectX in kernel model used by Windows XP and earlier was the anomaly by modern terms.

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#26
post #25

Earlier quoted context omitted.

Yes, and display drivers are in large part in user mode too: https://docs.microsoft.com/en-us/windows-hardware/drivers/di... This has been the case since Windows Vista WDDM.

So they are on Linux, macOS and other platforms. In fact the DirectX in kernel model used by Windows XP and earlier was the anomaly by modern terms.

I don’t understand why you argue with me. Moving the user-space is good. My point is that the direction should be moving to user-space, not tacking more and more on the kernel, especially for silly things such as DRM.

Re: About the security content of iOS 15.4.1 and iPadOS 15.4.1

#27

Earlier quoted context omitted.

It's a kext for decoding HEVC, H.264, and VP9.

Sounds to me like a terrible OS design, to have such arbitrary things as video decoding, require a kernel extension. Microsoft move drivers, such as GPU, to user space, to escape exactly issues like these. This is likely done for the sake of DRM, which is even worse. But SiDeLoADiNg is what is threatening users’ security.

Which OS kernel doesn't provide video decoding capabilities nowadays? At least Linux does, and most likely Windows too.

> This is likely done for the sake of DRM

The reason is hardware acceleration. No sane OS vendor is going to place every single piece of code in the kernel where DRM is involved.

> But SiDeLoADiNg

Not disagreeing, but do you have to bring it up on every single issue? I don't see the connection here.

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