Re: 2.2 PATCH: check return from copy_*_user in fs/pipe.c

["Zack Weinberg" <zackw@stanford.edu>]

Linus Torvalds wrote:
> If somebody passes in a bad pointer to a system call, you've just
> invoced the rule of "the kernel _may_ be nice to you, but the kernel
> might just consider you a moron and tell you it worked".
> 
> There is no "lost data" or anything else. You've screwed yourself, and
> you threw the data away. Don't blame the kernel.
> 
> And before you say "it has to return EFAULT", check the standards, and
> think about the case of libraries vs system calls - and how do you tell
> them apart?

My reading of the standard is that it has to either return EFAULT or
raise SIGSEGV.  But I am not expert in XPG4-ese.

Whether or not the standard requires anything, I would much rather
that the kernel not silently discard error conditions.

zw