Messages in this thread | | | Date | Wed, 14 Sep 2005 22:05:02 -0600 | From | "Nick Piggin" <> | Subject | Re: ptrace can't be transparent on readonly MAP_SHARED |
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>>>Andrea Arcangeli <andrea@suse.de> 09/15/05 7:24 am >>> > >About generating anonymous pages on top of map_shared that should be >fine with the vm, the way anon-vma works, it already happens for >map_private and it's not conceputally different for anon-vma to deal >with overlap with map-shared or map-private. So I don't think we need to >forbid ptrace (i.e. gdb) to write to a readonly map shared or stuff like >that. > >Comments welcome. (especially if you see any bug in my simpler approach
>please let me know because that's how I fixed the DoS in some kernel ;)
>thanks! >
I like the look of the patch.
I would like to go one step further and simply disallow writing to MAP_SHARED memory full stop. It eliminates so many corner cases and weird behaviour (ie. after writing to a readonly MAP_SHARED, the process will no longer see updates to the file).
Actually, maybe that's too much. I imagine on a shared memory application there would be use in changing writeable MAP_SHARED memory in a debugger. How about we disallow writing to readonly MAP_SHARED?
However going back a step - I still think Andrea's patch is nicer than what we have now.
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