Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH v2 8/8] exec: Use sane stack rlimit under secureexec | Date | Mon, 10 Jul 2017 00:57:31 -0700 |
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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 <keescook@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
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