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 <[email protected]> Signed-off-by: Kees Cook <[email protected]> Reviewed-by: James Morris <[email protected]> Acked-by: Serge Hallyn <[email protected]> --- fs/exec.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/exec.c b/fs/exec.c index 3ae8a40c587b..cddd2a2cbc1f 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1329,6 +1329,18 @@ 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; -- 2.7.4
