[PATCH] SELinux: extend task_kill hook to handle signals sent by AIO completion

This patch extends the security_task_kill hook to handle signals sent by AIO
completion.  In this case, the secid of the task responsible for the signal
needs to be obtained and saved earlier, so a security_task_getsecid() hook is
added, and then this saved value is passed subsequently to the extended
task_kill hook for use in checking.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/security.h

@@ -567,6 +567,9 @@ struct swap_info_struct;
  *	@p.
  *	@p contains the task_struct for the process.
  *	Return 0 if permission is granted.
+ * @task_getsecid:
+ *	Retrieve the security identifier of the process @p.
+ *	@p contains the task_struct for the process and place is into @secid.
  * @task_setgroups:
  *	Check permission before setting the supplementary group set of the
  *	current process.
@@ -615,6 +618,7 @@ struct swap_info_struct;
  *	@p contains the task_struct for process.
  *	@info contains the signal information.
  *	@sig contains the signal value.
+ *	@secid contains the sid of the process where the signal originated
  *	Return 0 if permission is granted.
  * @task_wait:
  *	Check permission before allowing a process to reap a child process @p
@@ -1219,6 +1223,7 @@ struct security_operations {
 	int (*task_setpgid) (struct task_struct * p, pid_t pgid);
 	int (*task_getpgid) (struct task_struct * p);
 	int (*task_getsid) (struct task_struct * p);
+	void (*task_getsecid) (struct task_struct * p, u32 * secid);
 	int (*task_setgroups) (struct group_info *group_info);
 	int (*task_setnice) (struct task_struct * p, int nice);
 	int (*task_setioprio) (struct task_struct * p, int ioprio);
@@ -1228,7 +1233,7 @@ struct security_operations {
 	int (*task_getscheduler) (struct task_struct * p);
 	int (*task_movememory) (struct task_struct * p);
 	int (*task_kill) (struct task_struct * p,
-			  struct siginfo * info, int sig);
+			  struct siginfo * info, int sig, u32 secid);
 	int (*task_wait) (struct task_struct * p);
 	int (*task_prctl) (int option, unsigned long arg2,
 			   unsigned long arg3, unsigned long arg4,
@@ -1839,6 +1844,11 @@ static inline int security_task_getsid (struct task_struct *p)
 	return security_ops->task_getsid (p);
 }
 
+static inline void security_task_getsecid (struct task_struct *p, u32 *secid)
+{
+	security_ops->task_getsecid (p, secid);
+}
+
 static inline int security_task_setgroups (struct group_info *group_info)
 {
 	return security_ops->task_setgroups (group_info);
@@ -1878,9 +1888,10 @@ static inline int security_task_movememory (struct task_struct *p)
 }
 
 static inline int security_task_kill (struct task_struct *p,
-				      struct siginfo *info, int sig)
+				      struct siginfo *info, int sig,
+				      u32 secid)
 {
-	return security_ops->task_kill (p, info, sig);
+	return security_ops->task_kill (p, info, sig, secid);
 }
 
 static inline int security_task_wait (struct task_struct *p)
@@ -2491,6 +2502,9 @@ static inline int security_task_getsid (struct task_struct *p)
 	return 0;
 }
 
+static inline void security_task_getsecid (struct task_struct *p, u32 *secid)
+{ }
+
 static inline int security_task_setgroups (struct group_info *group_info)
 {
 	return 0;
@@ -2530,7 +2544,8 @@ static inline int security_task_movememory (struct task_struct *p)
 }
 
 static inline int security_task_kill (struct task_struct *p,
-				      struct siginfo *info, int sig)
+				      struct siginfo *info, int sig,
+				      u32 secid)
 {
 	return 0;
 }

security/dummy.c

@@ -506,6 +506,9 @@ static int dummy_task_getsid (struct task_struct *p)
 	return 0;
 }
 
+static void dummy_task_getsecid (struct task_struct *p, u32 *secid)
+{ }
+
 static int dummy_task_setgroups (struct group_info *group_info)
 {
 	return 0;
@@ -548,7 +551,7 @@ static int dummy_task_wait (struct task_struct *p)
 }
 
 static int dummy_task_kill (struct task_struct *p, struct siginfo *info,
-			    int sig)
+			    int sig, u32 secid)
 {
 	return 0;
 }
@@ -981,6 +984,7 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, task_setpgid);
 	set_to_dummy_if_null(ops, task_getpgid);
 	set_to_dummy_if_null(ops, task_getsid);
+	set_to_dummy_if_null(ops, task_getsecid);
 	set_to_dummy_if_null(ops, task_setgroups);
 	set_to_dummy_if_null(ops, task_setnice);
 	set_to_dummy_if_null(ops, task_setioprio);

security/selinux/hooks.c

@@ -2644,6 +2644,11 @@ static int selinux_task_getsid(struct task_struct *p)
 	return task_has_perm(current, p, PROCESS__GETSESSION);
 }
 
+static void selinux_task_getsecid(struct task_struct *p, u32 *secid)
+{
+	selinux_get_task_sid(p, secid);
+}
+
 static int selinux_task_setgroups(struct group_info *group_info)
 {
 	/* See the comment for setuid above. */
@@ -2700,12 +2705,14 @@ static int selinux_task_movememory(struct task_struct *p)
 	return task_has_perm(current, p, PROCESS__SETSCHED);
 }
 
-static int selinux_task_kill(struct task_struct *p, struct siginfo *info, int sig)
+static int selinux_task_kill(struct task_struct *p, struct siginfo *info,
+				int sig, u32 secid)
 {
 	u32 perm;
 	int rc;
+	struct task_security_struct *tsec;
 
-	rc = secondary_ops->task_kill(p, info, sig);
+	rc = secondary_ops->task_kill(p, info, sig, secid);
 	if (rc)
 		return rc;
 
@@ -2716,8 +2723,12 @@ static int selinux_task_kill(struct task_struct *p, struct siginfo *info, int si
 		perm = PROCESS__SIGNULL; /* null signal; existence test */
 	else
 		perm = signal_to_av(sig);
-
-	return task_has_perm(current, p, perm);
+	tsec = p->security;
+	if (secid)
+		rc = avc_has_perm(secid, tsec->sid, SECCLASS_PROCESS, perm, NULL);
+	else
+		rc = task_has_perm(current, p, perm);
+	return rc;
 }
 
 static int selinux_task_prctl(int option,
@@ -4434,6 +4445,7 @@ static struct security_operations selinux_ops = {
 	.task_setpgid =			selinux_task_setpgid,
 	.task_getpgid =			selinux_task_getpgid,
 	.task_getsid =		        selinux_task_getsid,
+	.task_getsecid =		selinux_task_getsecid,
 	.task_setgroups =		selinux_task_setgroups,
 	.task_setnice =			selinux_task_setnice,
 	.task_setioprio =		selinux_task_setioprio,