Re: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel

From: Avi Kivity
Date: Sun Dec 28 2008 - 09:10:05 EST


(restoring cc list)

Andi Kleen wrote:
One of the other problems: NMIs and MCEs have the same problem with SYSCALL

This one however looks unsolvable. Userspace can point %rsp into arbitrary memory, issue a syscall, and hope for an nmi. Since we're in cpl 0 and are not using IST, the processor will not switch stacks, and the nmi stack frame will corrupt any memory the user chooses to point to.

Even without a malicious user, %rsp could legitimately point at unmapped memory.

I don't see how syscall could work on i386, and indeed:

vdso32.so-$(VDSO32-y) += int80
vdso32.so-$(CONFIG_COMPAT) += syscall
vdso32.so-$(VDSO32-y) += sysenter

It's disabled. Is that the reason?

--
error compiling committee.c: too many arguments to function

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