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 <keesc...@chromium.org>
---
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
