Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 10 Mar 2012 16:01:09 -0800 | Subject | Re: [PATCH 0/9] proc: protect /proc/<pid>/* files across execve |
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On Sat, Mar 10, 2012 at 3:25 PM, Djalal Harouni <tixxdz@opendz.org> wrote: > > 1) Use the target exec_id to bind files to their exec_id task: > > For the REG files /proc/<pid>/{environ,pagemap,mem} we set the exec_id > of the proc_file_private to the target task, and we continue with > permission checks at open time, later on each read/write call the > permission checks are done + check the target exec_id if it equals the > exec_id of the proc_file_private that was set at open time, in other words > we bind the file to its task's exec_id, this way new exec programs can not > operate on the passed fd.
So the exec_id approach was totally broken when it was used for /proc/<pid>/mem, is there any reason to believe it's a good idea now?
It's entirely predictable, and you can make the exec_id match by simply forking elsewhere and then passing the fd around using unix domain sockets, since the exec_id is just updated by incrementing a counter.
I would in general suggest strongly against using exec_id for anything that involves files. It isn't designed for that, it's designed for the whole "check the parent exec_id" thing for ptrace, where that whole "pass things around to another process" approach doesn't work.
Linus
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