From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Kees Cook To: Linus Torvalds Cc: Kees Cook , Andy Lutomirski , David Howells , Serge Hallyn , John Johansen , Casey Schaufler , "Eric W. Biederman" , Alexander Viro , Michal Hocko , Ben Hutchings , Hugh Dickins , Oleg Nesterov , "Jason A. Donenfeld" , Rik van Riel , James Morris , Greg Ungerer , Ingo Molnar , Nicolas Pitre , Stephen Smalley , Paul Moore , Vivek Goyal , =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Tetsuo Handa , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov Subject: [PATCH v2 8/8] exec: Use sane stack rlimit under secureexec Date: Mon, 10 Jul 2017 00:57:31 -0700 Message-Id: <1499673451-66160-9-git-send-email-keescook@chromium.org> In-Reply-To: <1499673451-66160-1-git-send-email-keescook@chromium.org> References: <1499673451-66160-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: For a secureexec, before memory layout selection has happened, reset the stack rlimit to something sane to avoid the caller having control over the resulting layouts. $ ulimit -s 8192 $ ulimit -s unlimited $ /bin/sh -c 'ulimit -s' unlimited $ sudo /bin/sh -c 'ulimit -s' 8192 Signed-off-by: Kees Cook --- fs/exec.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index e0186db02f90..1e3463854a16 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1343,6 +1343,16 @@ void setup_new_exec(struct linux_binprm * bprm) /* Make sure parent cannot signal privileged process. */ current->pdeath_signal = 0; + + /* + * For secureexec, reset the stack limit to sane default to + * avoid bad behavior from the prior rlimits. This has to + * happen before arch_pick_mmap_layout(), which examines + * RLIMIT_STACK, but after the point of no return to avoid + * needing to clean up the change on failure. + */ + if (current->signal->rlim[RLIMIT_STACK].rlim_cur > _STK_LIM) + current->signal->rlim[RLIMIT_STACK].rlim_cur = _STK_LIM; } arch_pick_mmap_layout(current->mm); -- 2.7.4