On Thu, Dec 3, 2015 at 1:12 PM, Arnd Bergmann [off-list ref] wrote:

On Thursday 03 December 2015 17:28:30 Lee Jones wrote:

quoted

quoted

Ah, interesting. I haven't tried myself, and just tried to read the
code. Maybe glibc already catches zero-length writes before it gets
into the kernel, or I just missed the part of the syscall that checks
for this.

Glibc is responsible indeed:

  http://osxr.org/glibc/source/io/write.c

Ok, so an attacker can force the stack overflow by calling
syscall(__NR_write, fd, p, 0) if that has any potential value,
but normal users won't hit this case.

It seems glibc might be the only libc implementation with this protection.

Regards,
Bjorn