Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
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Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#2Someone in the Phoronix comments wondered why not just map it (the kernel-assisted trampoline memory page) executable and not writeable, to avoid the attack surface but be significantly faster. I also wonder exactly why, admittedly I haven’t read the mailing list thread entirely but purely working on theory I wonder what the advantages of working on page fault is. Less abusable gadgets in memory? More flexibility? Perhaps additional Spectre-type mitigations?
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#3This is not just "Microsoft Engineer", it is Michael Larabel, the principal author of phoronix.com.
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#4This is not just "Microsoft Engineer", it is Michael Larabel, the principal author of phoronix.com.
Naw, that's just his byline. The Microsoft engineeer is Madhavan T. Venkataraman.
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#5This is not just "Microsoft Engineer", it is Michael Larabel, the principal author of phoronix.com.
> From: "Madhavan T. Venkataraman"
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#6Someone in the Phoronix comments wondered why not just map it (the kernel-assisted trampoline memory page) executable and not writeable, to avoid the attack surface but be significantly faster. I also wonder exactly why, admittedly I haven’t read the mailing list thread entirely but purely working on theory I wonder what the advantages of working on page fault is. Less abusable gadgets in memory? More flexibility? Pe…
Currently the page must be writeable at some point in order to create the trampoline.
A page fault is used as a way of executing the trampoline without the page having to be made executable/writable---the page fault handler recognises the page as a special trampoline page and handles the jump to the trampolines target address (which was previously registered using the new syscall).
Note that AFAICS this is unrelated to Spectre. The intended use is for constructing closures for use in FFI libraries such as libffi.
EDIT: I think I perhaps misunderstood your query---are you saying why not just make a system call where the kernel creates the page for you with the desired trampoline code and execute permissions?
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#7This is not just "Microsoft Engineer", it is Michael Larabel, the principal author of phoronix.com.
The person's name in the patch file is Madhavan T. Venkataraman. Try again next time.
Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#8Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#9Re: Microsoft Engineer Proposes “Trampfd” for Improving Linux Security
#10Does it really matter that he's a "Microsoft Engineer" or is that just thrown in there to ruffle old people's feathers?