Re: [RFC] "Text file busy" when overwriting libraries

Alan Cox
2001-10-15T11:48:59Z

> Just to reiterate I see this as a solution to two problems
> 1) It adds an additional safety check that shared libraries won't
> mutate under you.

Which prevents a user with rights doing so deliberately.

> 2) It allows user space access to the security policy information
> regarding executables. Allowing ld-linux.so to refust to
> execute binaries, and shared libaries on a filesystem mounted
> noexec.

Which is mostly useless anyway since anyone can write an ld-linux that
doesn't check providing the binary is readable. noexec is basically a weird
ancient unixism that is usless.

> My biggest unresolved issue is which numbers to choose for O_EXEC on
> every platform. As the DENYWRITE code is cleaner in open than in mmap.

And the fact that open has side effects.

Alan