Yama: handle 32-bit userspace prctl

When running a 64-bit kernel and receiving prctls from a 32-bit
userspace, the "-1" used as an unsigned long will end up being
misdetected. The kernel is looking for 0xffffffffffffffff instead of
0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
to handle this translation itself. As such, support either value as
meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Johansen <john.johansen@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: James Morris <james.l.morris@oracle.com>

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 9ca43c1ea630772cc50f82e684b6e0e8eb1b8e2e..01d3b44b62c14860be5bdccc9028fab4f66de5bd 100644 (file)
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -143,7 +143,7 @@ int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
                if (arg2 == 0) {
                        yama_ptracer_del(NULL, myself);
                        rc = 0;
-               } else if (arg2 == PR_SET_PTRACER_ANY) {
+               } else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
                        rc = yama_ptracer_add(NULL, myself);
                } else {
                        struct task_struct *tracer;