path: root/security
diff options
authorJosh Stone <jistone@redhat.com>2016-12-02 15:49:43 -0800
committerJames Morris <james.l.morris@oracle.com>2016-12-05 11:48:01 +1100
commit50523a29d900d5a403e0352d3d7aeda6a33df25c (patch)
tree4c279a19e9a0f4521212bf444a939bb83c8d1915 /security
parent9430066a15d6f55a3d008a6f99bb462480870207 (diff)
Yama: allow access for the current ptrace parent
Under ptrace_scope=1, it's possible to have a tracee that is already ptrace-attached, but is no longer a direct descendant. For instance, a forking daemon will be re-parented to init, losing its ancestry to the tracer that launched it. The tracer can continue using ptrace in that state, but it will be denied other accesses that check PTRACE_MODE_ATTACH, like process_vm_rw and various procfs files. There's no reason to prevent such access for a tracer that already has ptrace control anyway. This patch adds a case to ptracer_exception_found to allow access for any task in the same thread group as the current ptrace parent. Signed-off-by: Josh Stone <jistone@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: James Morris <james.l.morris@oracle.com> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: linux-security-module@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'security')
1 files changed, 15 insertions, 1 deletions
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 0309f2111c70..968e5e0a3f81 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -309,7 +309,7 @@ static int task_is_descendant(struct task_struct *parent,
* @tracer: the task_struct of the process attempting ptrace
* @tracee: the task_struct of the process to be ptraced
- * Returns 1 if tracer has is ptracer exception ancestor for tracee.
+ * Returns 1 if tracer has a ptracer exception ancestor for tracee.
static int ptracer_exception_found(struct task_struct *tracer,
struct task_struct *tracee)
@@ -320,6 +320,18 @@ static int ptracer_exception_found(struct task_struct *tracer,
bool found = false;
+ /*
+ * If there's already an active tracing relationship, then make an
+ * exception for the sake of other accesses, like process_vm_rw().
+ */
+ parent = ptrace_parent(tracee);
+ if (parent != NULL && same_thread_group(parent, tracer)) {
+ rc = 1;
+ goto unlock;
+ }
+ /* Look for a PR_SET_PTRACER relationship. */
if (!thread_group_leader(tracee))
tracee = rcu_dereference(tracee->group_leader);
list_for_each_entry_rcu(relation, &ptracer_relations, node) {
@@ -334,6 +346,8 @@ static int ptracer_exception_found(struct task_struct *tracer,
if (found && (parent == NULL || task_is_descendant(parent, tracer)))
rc = 1;
return rc;