Messages in this thread | | | Date | Fri, 28 Aug 1998 10:42:06 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: Anybody out there? (ETXTBSY) |
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On 28 Aug 1998, Andi Kleen wrote: > > > The reason MAP_EXECUTABLE isn't exported is programs like this: > > > fd = open("/var/spool/utmp"); > > mmap( ... fd ... MAP_EXECUTABLE ...); > > sleep(forever); /* nobody is able to log in */ > > > which used to actually happen. > > How about only allowing MAP_EXECUTABLE on files that have the x bit set? > This would prevent this attack, and ETXTBSY could be properly implemented. > > Or do I miss something here?
There are potentially executable files that we still don't want to allow MAP_EXECUTABLE on, but yes, that general approach would also have worked. The reason I disabled MAP_EXECUTABLE completely from user space was that I had patches for it, not because I felt strongly for that being a particularly good thing to do.
I actually like best the suggestion somebody had which was to do it automatically when both the file and the mapping are executable, and continue to use the MAP_EXECUTABLE flag as a purely kernel internal one.
Linus
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