Messages in this thread |  | | Date | Fri, 6 Nov 2015 12:55:08 -0800 | Subject | Re: [PATCH 4.1 11/86] iommu/amd: Fix BUG when faulting a PROT_NONE VMA | From | Linus Torvalds <> |
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On Fri, Nov 6, 2015 at 12:49 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > And some "handle_mm_fault would BUG_ON()" comment is just bogus. It's > not handle_mm_fault()'s case that you called it without checking > proper permissions.
Side note: as to why handle_mm_fault() doesn't just do things itself, there's a historical situation where we used to let people do things in ptrace() that they couldn't do directly, and punch through protections (and turn shared read-only pages into a dirty private page).
So the permissions checking was up to the caller, because some callers could do things that other callers could not.
I *think* we have gotten rid of all those cases, and I guess we could consider just making handle_mm_fault() itself stricter. But that's the historical background on why callers need to check this.
Adding linux-mm to the cc, to see if anybody there has some comments wrt just moving all the EFAULT handling into handle_mm_fault() and relaxing the caller requirements.
Linus
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