Messages in this thread | | | Date | Tue, 3 Apr 2012 23:32:04 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE |
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On Tue, Apr 03, 2012 at 11:16:31AM -0700, Matt Helsley wrote: > On Tue, Apr 03, 2012 at 09:10:20AM +0400, Konstantin Khlebnikov wrote: > > Matt Helsley wrote: > > >On Sat, Mar 31, 2012 at 10:13:24PM +0200, Oleg Nesterov wrote: > > >>On 03/31, Konstantin Khlebnikov wrote: > > >>> > > >>>comment from v2.6.25-6245-g925d1c4 ("procfs task exe symlink"), > > >>>where all this stuff was introduced: > > >>> > > >>>>... > > >>>>This avoids pinning the mounted filesystem. > > >>> > > >>>So, this logic is hooked into every file mmap/unmmap and vma split/merge just to > > >>>fix some hypothetical pinning fs from umounting by mm which already unmapped all > > >>>its executable files, but still alive. Does anyone know any real world example? > > >> > > >>This is the question to Matt. > > > > > >This is where I got the scenario: > > > > > >https://lkml.org/lkml/2007/7/12/398 > > > > Cyrill Gogcunov's patch "c/r: prctl: add ability to set new mm_struct::exe_file" > > gives userspace ability to unpin vfsmount explicitly. > > Doesn't that break the semantics of the kernel ABI?
Which one? exe_file can be changed iif there is no MAP_EXECUTABLE left. Still, once assigned (via this prctl) the mm_struct::exe_file can't be changed again, until program exit.
Cyrill
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