[patch] Fix BZ 19165 -- overflow in fread / fwrite

[Florian Weimer]

On 02/11/2016 03:26 AM, Rich Felker wrote:
> I think the problem may be even worse than we all expected. I've been
> trying to fix the corresponding issue in musl, and it looks like the
> _kernel_ is spuriously failing these reads with EFAULT by pre-checking
> the validity of the potential destination address range rather than
> only checking if there would actually be data to copy.

Yes, system call behavior in this area is fairly regular: if a memory
region is passed, it is checked for validity as a whole, and not just
for the parts that are actually needed.  By now, this is part of the
user space interface, and probably cannot change without breaking
backwards compatibility.

Florian