Messages in this thread | | | Date | Sat, 24 Dec 2005 09:16:48 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: More info for DSM w/r/t sunffb on 2.6.15-rc6 |
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On Sat, 24 Dec 2005, Linus Torvalds wrote: > On Fri, 23 Dec 2005, David S. Miller wrote: > > > > + if (!(vma->vm_flags & VM_SHARED)) > > + return -EINVAL; > > + > > Side note - as I explained to Nick the other week, VM_SHARED really means > "shared _writable_" mapping, so you're now disallowing a shared read-only > open too. > > Which may be fine, of course. Especially if sbusfb always ends up giving a > writable pfn-mapping. But I wanted to check that that was what you meant > to do. > > To test for MAP_SHARED, either do the is_cow_mapping() thing, or check > the VM_MAYSHARE bit.
I wondered over that too. Concluded that at the moment it's right for the test to be on VM_SHARED, because it's secretly giving away shared write permission. But in future, once that's been corrected, such checks would do better to check for VM_MAYSHARE (i.e. reject all MAP_PRIVATE).
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