Well it was worked around, not properly fixed. This patch fixes it properly.
The problem of the original workaround is that it wouldn't print the vma
now in many cases because it couldn't take the semaphore.
The workaround was right back then because it was shortly before
the release, but it was always a ward that needed fixing properly.
I believe it was a good idea anyways because there were always
some possible problems with not being able to sleep in these
exception handlers.
Yes, but that's fine.
That's not possible generally. None of these interrupts can
nest in a normal kernel.
Do you refer to the DEBUG_STACK ist add/dec? That is not needed
for anything in tree to my knowledge.
The IST is restored again after the handler. You're right that strictly
wouldn't be needed and could be avoided, but i don't think it's exploitable
in any ways.
Regarding user controlled pt_regs: I think you're forgetting that
x86-64 doesn't have vm86 mode and that we can always trust pt_regs
segment indexes. On i386 you would be right, but not here.
-Andi
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