[TOMOYO #6 retry 21/21] Add signal hooks at sleepable location.

[Kentaro Takeda]

This patch adds LSM hooks for sending signal.

   * task_kill_unlocked is added in sys_kill
   * task_tkill_unlocked is added in sys_tkill
   * task_tgkill_unlocked is added in sys_tgkill

We know sleepable hooks are racy.
But we want to add sleepable hooks because TOMOYO Linux supports
"delayed enforcing" mode which allows administrator judge interactively.

You can try TOMOYO Linux without this patch, but in that case, you
can't use access control functionality for restricting signal transmission.

Signed-off-by: Kentaro Takeda <takedakn@xxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/security.h |   41 +++++++++++++++++++++++++++++++++++++++++
 kernel/signal.c          |   17 +++++++++++++++++
 security/dummy.c         |   18 ++++++++++++++++++
 security/security.c      |   15 +++++++++++++++
 4 files changed, 91 insertions(+)

--- linux-2.6-mm.orig/include/linux/security.h
+++ linux-2.6-mm/include/linux/security.h
@@ -674,6 +674,25 @@ struct request_sock;
  *	@sig contains the signal value.
  *	@secid contains the sid of the process where the signal originated
  *	Return 0 if permission is granted.
+ * @task_kill_unlocked:
+ *	Check permission before sending signal @sig to the process of @pid
+ *	with sys_kill.
+ *	@pid contains the pid of target process.
+ *	@sig contains the signal value.
+ *	Return 0 if permission is granted.
+ * @task_tkill_unlocked:
+ *	Check permission before sending signal @sig to the process of @pid
+ *	with sys_tkill.
+ *	@pid contains the pid of target process.
+ *	@sig contains the signal value.
+ *	Return 0 if permission is granted.
+ * @task_tgkill_unlocked:
+ *	Check permission before sending signal @sig to the process of @pid
+ *	with sys_tgkill.
+ *	@tgid contains the thread group id.
+ *	@pid contains the pid of target process.
+ *	@sig contains the signal value.
+ *	Return 0 if permission is granted.
  * @task_wait:
  *	Check permission before allowing a process to reap a child process @p
  *	and collect its status information.
@@ -1364,6 +1383,9 @@ struct security_operations {
 	int (*task_movememory) (struct task_struct * p);
 	int (*task_kill) (struct task_struct * p,
 			  struct siginfo * info, int sig, u32 secid);
+	int (*task_kill_unlocked) (int pid, int sig);
+	int (*task_tkill_unlocked) (int pid, int sig);
+	int (*task_tgkill_unlocked) (int tgid, int pid, int sig);
 	int (*task_wait) (struct task_struct * p);
 	int (*task_prctl) (int option, unsigned long arg2,
 			   unsigned long arg3, unsigned long arg4,
@@ -1622,6 +1644,10 @@ int security_task_getscheduler(struct ta
 int security_task_movememory(struct task_struct *p);
 int security_task_kill(struct task_struct *p, struct siginfo *info,
 			int sig, u32 secid);
+#define __HAVE_LSM_TASK_KILL_UNLOCKED
+int security_task_kill_unlocked(int pid, int sig);
+int security_task_tkill_unlocked(int pid, int sig);
+int security_task_tgkill_unlocked(int tgid, int pid, int sig);
 int security_task_wait(struct task_struct *p);
 int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 			 unsigned long arg4, unsigned long arg5);
@@ -2168,6 +2194,21 @@ static inline int security_task_kill (st
 	return cap_task_kill(p, info, sig, secid);
 }
 
+static inline int security_task_kill_unlocked(int pid, int sig)
+{
+	return 0;
+}
+
+static inline int security_task_tkill_unlocked(int pid, int sig)
+{
+	return 0;
+}
+
+static inline int security_task_tgkill_unlocked(int tgid, int pid, int sig)
+{
+	return 0;
+}
+
 static inline int security_task_wait (struct task_struct *p)
 {
 	return 0;
--- linux-2.6-mm.orig/kernel/signal.c
+++ linux-2.6-mm/kernel/signal.c
@@ -2219,6 +2219,11 @@ asmlinkage long
 sys_kill(int pid, int sig)
 {
 	struct siginfo info;
+	int ret;
+
+	ret = security_task_kill_unlocked(pid, sig);
+	if (ret)
+		return ret;
 
 	info.si_signo = sig;
 	info.si_errno = 0;
@@ -2274,10 +2279,16 @@ static int do_tkill(int tgid, int pid, i
  */
 asmlinkage long sys_tgkill(int tgid, int pid, int sig)
 {
+	int ret;
+
 	/* This is only valid for single tasks */
 	if (pid <= 0 || tgid <= 0)
 		return -EINVAL;
 
+	ret = security_task_tgkill_unlocked(tgid, pid, sig);
+	if (ret)
+		return ret;
+
 	return do_tkill(tgid, pid, sig);
 }
 
@@ -2287,10 +2298,16 @@ asmlinkage long sys_tgkill(int tgid, int
 asmlinkage long
 sys_tkill(int pid, int sig)
 {
+	int ret;
+
 	/* This is only valid for single tasks */
 	if (pid <= 0)
 		return -EINVAL;
 
+	ret = security_task_tkill_unlocked(pid, sig);
+	if (ret)
+		return ret;
+
 	return do_tkill(0, pid, sig);
 }
 
--- linux-2.6-mm.orig/security/dummy.c
+++ linux-2.6-mm/security/dummy.c
@@ -599,6 +599,21 @@ static int dummy_task_kill (struct task_
 	return 0;
 }
 
+static int dummy_task_kill_unlocked(int pid, int sig)
+{
+	return 0;
+}
+
+static int dummy_task_tkill_unlocked(int pid, int sig)
+{
+	return 0;
+}
+
+static int dummy_task_tgkill_unlocked(int tgid, int pid, int sig)
+{
+	return 0;
+}
+
 static int dummy_task_prctl (int option, unsigned long arg2, unsigned long arg3,
 			     unsigned long arg4, unsigned long arg5)
 {
@@ -1104,6 +1119,9 @@ void security_fixup_ops (struct security
 	set_to_dummy_if_null(ops, task_movememory);
 	set_to_dummy_if_null(ops, task_wait);
 	set_to_dummy_if_null(ops, task_kill);
+	set_to_dummy_if_null(ops, task_kill_unlocked);
+	set_to_dummy_if_null(ops, task_tkill_unlocked);
+	set_to_dummy_if_null(ops, task_tgkill_unlocked);
 	set_to_dummy_if_null(ops, task_prctl);
 	set_to_dummy_if_null(ops, task_reparent_to_init);
  	set_to_dummy_if_null(ops, task_to_inode);
--- linux-2.6-mm.orig/security/security.c
+++ linux-2.6-mm/security/security.c
@@ -682,6 +682,21 @@ int security_task_kill(struct task_struc
 	return security_ops->task_kill(p, info, sig, secid);
 }
 
+int security_task_kill_unlocked(int pid, int sig)
+{
+	return security_ops->task_kill_unlocked(pid, sig);
+}
+
+int security_task_tkill_unlocked(int pid, int sig)
+{
+	return security_ops->task_tkill_unlocked(pid, sig);
+}
+
+int security_task_tgkill_unlocked(int tgid, int pid, int sig)
+{
+	return security_ops->task_tgkill_unlocked(tgid, pid, sig);
+}
+
 int security_task_wait(struct task_struct *p)
 {
 	return security_ops->task_wait(p);

-- 
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