From: Kees Cook Date: Tue, 18 Jul 2017 22:25:35 +0000 (-0700) Subject: exec: Use sane stack rlimit under secureexec X-Git-Tag: v4.14-rc1~98^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=64701dee4178eb4a771b8b36cd86560f5b0e2460;p=platform%2Fkernel%2Flinux-exynos.git exec: Use sane stack rlimit under secureexec 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 Cc: Linus Torvalds Signed-off-by: Kees Cook Reviewed-by: James Morris Acked-by: Serge Hallyn --- diff --git a/fs/exec.c b/fs/exec.c index 3006c1c..3235cbd 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1350,6 +1350,18 @@ void setup_new_exec(struct linux_binprm * bprm) */ bprm->secureexec |= bprm->cap_elevated; + if (bprm->secureexec) { + /* + * 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); current->sas_ss_sp = current->sas_ss_size = 0;