binfmt_elf: safely increment argv pointers
authorKees Cook <keescook@chromium.org>
Mon, 10 Jul 2017 22:52:54 +0000 (15:52 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 10 Jul 2017 23:32:36 +0000 (16:32 -0700)
commit67c6777a5d331dda32a4c4a1bf0cac85bdaaaed8
treec5ae9869b8e0a3e81091bb08597ea54346655824
parenta73dc5370e153ac63718d850bddf0c9aa9d871e6
binfmt_elf: safely increment argv pointers

When building the argv/envp pointers, the envp is needlessly
pre-incremented instead of just continuing after the argv pointers are
finished.  In some (likely impossible) race where the strings could be
changed from userspace between copy_strings() and here, it might be
possible to confuse the envp position.  Instead, just use sp like
everything else.

Link: http://lkml.kernel.org/r/20170622173838.GA43308@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Qualys Security Advisory <qsa@qualys.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/binfmt_elf.c