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SubjectRe: bug in write(2) system call.
Chris Wedgwood <> said:


> Basically... if you pass bogus addresses and pointers to the kernel,
> depending on what OS and version you are running, you might get an
> EFAULT and you might not.

This is (somewhat) OK.

> There is no wrong or right way - and no simple fix other than DON'T

You should try not to, but the kernel _can't_ just believe in your
guarantees. For all it knows, you might be Kubys ;-)

> In linux 2.0.x and more traditional kernels, the verify_area checks
> will determine the address of bogus before reading or writing any
> data, under 2.1.x and I think also NetBSD, if the start of the memory
> range you spcific is legitimate, some data will be read and written.

In the 2.1.xx kernels this mechanism was replaced by a nifty, no-overhead
use of the MM to do the same thing: No checks, but if an illegal access is
attempted, the kernel gets an exception. Look at your nearest Documentation
Dr. Horst H. von Brand
Departamento de Informatica Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria +56 32 654239
Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513

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