Re: copy_from_user() fix

Martin Mares (mj@atrey.karlin.mff.cuni.cz)
Wed, 26 Aug 1998 13:59:31 +0200

> Consider a userland pointer verification library that worked in about
> 10 lines of code by passing the pointer in question to a sys_write()
> call to /dev/null... but this wouldn't work actually these days due to
> how the kernel won't even verify the pointer in this case.

It would probably work on several systems, but all standards I know
of say that passing of invalid pointer to syscalls has totally undefined
effect. Dirty, unportable, hic sunt leones :))

Anyway, it might be interesting to implement a reliable way how to
check address ranges (a syscall or maybe a ioctl on /proc/self/mem?)...

Have a nice fortnight

-- 
Martin `MJ' Mares   <mj@ucw.cz>   http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
"A LISP programmer knows value of everything, but cost of nothing."


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