exec: Use sane stack rlimit under secureexec (64701dee) · Commits · e / devices / android_kernel_fairphone_FP5

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 <torvalds@linux-foundation.org> Signed-off-by:

Kees Cook <keescook@chromium.org> Reviewed-by:

James Morris <james.l.morris@oracle.com> Acked-by:

Serge Hallyn <serge@hallyn.com>

fs/exec.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -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;