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-rw-r--r--security/yama/Kconfig8
-rw-r--r--security/yama/yama_lsm.c153
2 files changed, 125 insertions, 36 deletions
diff --git a/security/yama/Kconfig b/security/yama/Kconfig
index 51d6709d8bb..20ef5143c0c 100644
--- a/security/yama/Kconfig
+++ b/security/yama/Kconfig
@@ -11,3 +11,11 @@ config SECURITY_YAMA
Further information can be found in Documentation/security/Yama.txt.
If you are unsure how to answer this question, answer N.
+
+config SECURITY_YAMA_STACKED
+ bool "Yama stacked with other LSMs"
+ depends on SECURITY_YAMA
+ default n
+ help
+ When Yama is built into the kernel, force it to stack with the
+ selected primary LSM.
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 83554ee8a58..13c88fbcf03 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -17,6 +17,7 @@
#include <linux/ptrace.h>
#include <linux/prctl.h>
#include <linux/ratelimit.h>
+#include <linux/workqueue.h>
#define YAMA_SCOPE_DISABLED 0
#define YAMA_SCOPE_RELATIONAL 1
@@ -29,12 +30,37 @@ static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
struct ptrace_relation {
struct task_struct *tracer;
struct task_struct *tracee;
+ bool invalid;
struct list_head node;
+ struct rcu_head rcu;
};
static LIST_HEAD(ptracer_relations);
static DEFINE_SPINLOCK(ptracer_relations_lock);
+static void yama_relation_cleanup(struct work_struct *work);
+static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);
+
+/**
+ * yama_relation_cleanup - remove invalid entries from the relation list
+ *
+ */
+static void yama_relation_cleanup(struct work_struct *work)
+{
+ struct ptrace_relation *relation;
+
+ spin_lock(&ptracer_relations_lock);
+ rcu_read_lock();
+ list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+ if (relation->invalid) {
+ list_del_rcu(&relation->node);
+ kfree_rcu(relation, rcu);
+ }
+ }
+ rcu_read_unlock();
+ spin_unlock(&ptracer_relations_lock);
+}
+
/**
* yama_ptracer_add - add/replace an exception for this tracer/tracee pair
* @tracer: the task_struct of the process doing the ptrace
@@ -48,32 +74,34 @@ static DEFINE_SPINLOCK(ptracer_relations_lock);
static int yama_ptracer_add(struct task_struct *tracer,
struct task_struct *tracee)
{
- int rc = 0;
- struct ptrace_relation *added;
- struct ptrace_relation *entry, *relation = NULL;
+ struct ptrace_relation *relation, *added;
added = kmalloc(sizeof(*added), GFP_KERNEL);
if (!added)
return -ENOMEM;
- spin_lock_bh(&ptracer_relations_lock);
- list_for_each_entry(entry, &ptracer_relations, node)
- if (entry->tracee == tracee) {
- relation = entry;
- break;
+ added->tracee = tracee;
+ added->tracer = tracer;
+ added->invalid = false;
+
+ spin_lock(&ptracer_relations_lock);
+ rcu_read_lock();
+ list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+ if (relation->invalid)
+ continue;
+ if (relation->tracee == tracee) {
+ list_replace_rcu(&relation->node, &added->node);
+ kfree_rcu(relation, rcu);
+ goto out;
}
- if (!relation) {
- relation = added;
- relation->tracee = tracee;
- list_add(&relation->node, &ptracer_relations);
}
- relation->tracer = tracer;
- spin_unlock_bh(&ptracer_relations_lock);
- if (added != relation)
- kfree(added);
+ list_add_rcu(&added->node, &ptracer_relations);
- return rc;
+out:
+ rcu_read_unlock();
+ spin_unlock(&ptracer_relations_lock);
+ return 0;
}
/**
@@ -84,23 +112,30 @@ static int yama_ptracer_add(struct task_struct *tracer,
static void yama_ptracer_del(struct task_struct *tracer,
struct task_struct *tracee)
{
- struct ptrace_relation *relation, *safe;
+ struct ptrace_relation *relation;
+ bool marked = false;
- spin_lock_bh(&ptracer_relations_lock);
- list_for_each_entry_safe(relation, safe, &ptracer_relations, node)
+ rcu_read_lock();
+ list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+ if (relation->invalid)
+ continue;
if (relation->tracee == tracee ||
(tracer && relation->tracer == tracer)) {
- list_del(&relation->node);
- kfree(relation);
+ relation->invalid = true;
+ marked = true;
}
- spin_unlock_bh(&ptracer_relations_lock);
+ }
+ rcu_read_unlock();
+
+ if (marked)
+ schedule_work(&yama_relation_work);
}
/**
* yama_task_free - check for task_pid to remove from exception list
* @task: task being removed
*/
-static void yama_task_free(struct task_struct *task)
+void yama_task_free(struct task_struct *task)
{
yama_ptracer_del(task, task);
}
@@ -116,7 +151,7 @@ static void yama_task_free(struct task_struct *task)
* Return 0 on success, -ve on error. -ENOSYS is returned when Yama
* does not handle the given option.
*/
-static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5)
{
int rc;
@@ -143,7 +178,7 @@ static 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;
@@ -217,21 +252,22 @@ static int ptracer_exception_found(struct task_struct *tracer,
struct task_struct *parent = NULL;
bool found = false;
- spin_lock_bh(&ptracer_relations_lock);
rcu_read_lock();
if (!thread_group_leader(tracee))
tracee = rcu_dereference(tracee->group_leader);
- list_for_each_entry(relation, &ptracer_relations, node)
+ list_for_each_entry_rcu(relation, &ptracer_relations, node) {
+ if (relation->invalid)
+ continue;
if (relation->tracee == tracee) {
parent = relation->tracer;
found = true;
break;
}
+ }
if (found && (parent == NULL || task_is_descendant(parent, tracer)))
rc = 1;
rcu_read_unlock();
- spin_unlock_bh(&ptracer_relations_lock);
return rc;
}
@@ -243,7 +279,7 @@ static int ptracer_exception_found(struct task_struct *tracer,
*
* Returns 0 if following the ptrace is allowed, -ve on error.
*/
-static int yama_ptrace_access_check(struct task_struct *child,
+int yama_ptrace_access_check(struct task_struct *child,
unsigned int mode)
{
int rc;
@@ -262,14 +298,18 @@ static int yama_ptrace_access_check(struct task_struct *child,
/* No additional restrictions. */
break;
case YAMA_SCOPE_RELATIONAL:
+ rcu_read_lock();
if (!task_is_descendant(current, child) &&
!ptracer_exception_found(current, child) &&
- !ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+ !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;
+ rcu_read_unlock();
break;
case YAMA_SCOPE_CAPABILITY:
- if (!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+ rcu_read_lock();
+ if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;
+ rcu_read_unlock();
break;
case YAMA_SCOPE_NO_ATTACH:
default:
@@ -279,24 +319,61 @@ static int yama_ptrace_access_check(struct task_struct *child,
}
if (rc) {
- char name[sizeof(current->comm)];
printk_ratelimited(KERN_NOTICE
"ptrace of pid %d was attempted by: %s (pid %d)\n",
- child->pid,
- get_task_comm(name, current),
- current->pid);
+ child->pid, current->comm, current->pid);
}
return rc;
}
+/**
+ * yama_ptrace_traceme - validate PTRACE_TRACEME calls
+ * @parent: task that will become the ptracer of the current task
+ *
+ * Returns 0 if following the ptrace is allowed, -ve on error.
+ */
+int yama_ptrace_traceme(struct task_struct *parent)
+{
+ int rc;
+
+ /* If standard caps disallows it, so does Yama. We should
+ * only tighten restrictions further.
+ */
+ rc = cap_ptrace_traceme(parent);
+ if (rc)
+ return rc;
+
+ /* Only disallow PTRACE_TRACEME on more aggressive settings. */
+ switch (ptrace_scope) {
+ case YAMA_SCOPE_CAPABILITY:
+ if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
+ rc = -EPERM;
+ break;
+ case YAMA_SCOPE_NO_ATTACH:
+ rc = -EPERM;
+ break;
+ }
+
+ if (rc) {
+ printk_ratelimited(KERN_NOTICE
+ "ptraceme of pid %d was attempted by: %s (pid %d)\n",
+ current->pid, parent->comm, parent->pid);
+ }
+
+ return rc;
+}
+
+#ifndef CONFIG_SECURITY_YAMA_STACKED
static struct security_operations yama_ops = {
.name = "yama",
.ptrace_access_check = yama_ptrace_access_check,
+ .ptrace_traceme = yama_ptrace_traceme,
.task_prctl = yama_task_prctl,
.task_free = yama_task_free,
};
+#endif
#ifdef CONFIG_SYSCTL
static int yama_dointvec_minmax(struct ctl_table *table, int write,
@@ -343,13 +420,17 @@ static struct ctl_table yama_sysctl_table[] = {
static __init int yama_init(void)
{
+#ifndef CONFIG_SECURITY_YAMA_STACKED
if (!security_module_enable(&yama_ops))
return 0;
+#endif
printk(KERN_INFO "Yama: becoming mindful.\n");
+#ifndef CONFIG_SECURITY_YAMA_STACKED
if (register_security(&yama_ops))
panic("Yama: kernel registration failed.\n");
+#endif
#ifdef CONFIG_SYSCTL
if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-10 19:19:59 +0000