Messages in this thread | | | Date | Thu, 29 Apr 2021 18:45:49 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v26 22/30] x86/cet/shstk: Add user-mode shadow stack support |
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On Thu, Apr 29, 2021 at 09:17:06AM -0700, Yu, Yu-cheng wrote: > The lock applies to both shadow stack and ibt. So maybe just "locked"?
Sure.
> vm_munmap() returns error as the following: > > (1) -EINVAL: address/size/alignment is wrong. > For shadow stack, the kernel keeps track of it, this cannot/should not > happen.
You mean nothing might corrupt
cet->shstk_base cet->shstk_size
?
I can't count the ways I've heard "should not happen" before and then it happening anyway.
So probably not but we better catch stuff like that instead of leaking.
> Should it happen, it is a bug.
Ack.
> The kernel can probably do WARN().
Most definitely WARN. You need to catch funsies like that. But WARN_ONCE should be enough for now.
> (2) -ENOMEM: when doing __split_vma()/__vma_adjust(), kmem_cache_alloc() > fails. > Not much we can do. Perhaps WARN()?
You got it.
Bottom line is: if you can check for this and it is cheap, then definitely. Code changes, gets rewritten, reorganized, the old assertions change significance, and so on...
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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