On Thu, 29 Mar 2007, Jan Engelhardt wrote:
>
> I have to disagree, since wrapping it into a struct and copying the struct
> in kernelspace from userspace requires more code.
Not just more code, but more security issues too.
Passing system call arguments by value means that there are no subtle
security issues - the value you use is the value you got. But once you
pass-by-reference, you have to make damn sure that you do the proper user
space accesses and verify the pointer correctly.
User-space (aka "user-supplied") pointers are just more dangerous. We
obviously can't avoid them, but they need much more care than just a
random value directly passed in a register.
Linus
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