On Thu, 28 Apr 2016 21:04:18 +0200 Mathias Krause <mini...@googlemail.com> wrote:
> If /proc/<PID>/environ gets read before the envp[] array is fully set > up in create_{aout,elf,elf_fdpic,flat}_tables(), we might end up trying > to read more bytes than are actually written, as env_start will already > be set but env_end will still be zero, making the range calculation > underflow, allowing to read beyond the end of what has been written. > > Fix this as it is done for /proc/<PID>/cmdline by testing env_end for > zero. It is, apparently, intentionally set last in create_*_tables(). > > This bug was found by the PaX size_overflow plugin that detected the > arithmetic underflow of 'this_len = env_end - (env_start + src)' when > env_end is still zero. So what are the implications of this? From my reading, a craftily constructed application could occasionally read arbitrarily large amounts of kernel memory?