[PATCH 4/5] ipc: add new MSG_SET command for sys_msgctl() call

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

New MSG_SET command will be interpreted exactly as IPC_SET, but also will
update key, cuid and cgid values. IOW, it allows to change existent key value.
The fact, that key is not used is checked before update. Otherwise -EEXIST is
returned.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

---
 include/linux/msg.h        |    1 +
 ipc/compat.c               |    1 +
 ipc/msg.c                  |   13 +++++++++++--
 security/selinux/hooks.c   |    1 +
 security/smack/smack_lsm.c |    1 +
 5 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/msg.h b/include/linux/msg.h
index 56abf15..6689e73 100644
--- a/include/linux/msg.h
+++ b/include/linux/msg.h
@@ -6,6 +6,7 @@
 /* ipcs ctl commands */
 #define MSG_STAT 11
 #define MSG_INFO 12
+#define MSG_SET  13
 
 /* msgrcv options */
 #define MSG_NOERROR     010000  /* no error if message is too big */
diff --git a/ipc/compat.c b/ipc/compat.c
index fc378d9..20d639e 100644
--- a/ipc/compat.c
+++ b/ipc/compat.c
@@ -439,6 +439,7 @@ long compat_sys_msgctl(int first, int second, void __user *uptr)
 		break;
 
 	case IPC_SET:
+	case MSG_SET:
 		if (version == IPC_64) {
 			err = get_compat_msqid64(&m64, uptr);
 		} else {
diff --git a/ipc/msg.c b/ipc/msg.c
index fc98723..303362b 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -391,6 +391,9 @@ copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 		out->msg_perm.uid      	= tbuf_old.msg_perm.uid;
 		out->msg_perm.gid      	= tbuf_old.msg_perm.gid;
 		out->msg_perm.mode     	= tbuf_old.msg_perm.mode;
+		out->msg_perm.cuid	= tbuf_old.msg_perm.cuid;
+		out->msg_perm.cgid	= tbuf_old.msg_perm.cgid;
+		out->msg_perm.key	= tbuf_old.msg_perm.key;
 
 		if (tbuf_old.msg_qbytes == 0)
 			out->msg_qbytes	= tbuf_old.msg_lqbytes;
@@ -417,12 +420,13 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 	struct msg_queue *msq;
 	int err;
 
-	if (cmd == IPC_SET) {
+	if (cmd == IPC_SET || cmd == MSG_SET) {
 		if (copy_msqid_from_user(&msqid64, buf, version))
 			return -EFAULT;
 	}
 
-	ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
+	ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid,
+			       (cmd != MSG_SET) ? : IPC_SET,
 			       &msqid64.msg_perm, msqid64.msg_qbytes);
 	if (IS_ERR(ipcp))
 		return PTR_ERR(ipcp);
@@ -438,6 +442,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 		freeque(ns, ipcp);
 		goto out_up;
 	case IPC_SET:
+	case MSG_SET:
 		if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 		    !capable(CAP_SYS_RESOURCE)) {
 			err = -EPERM;
@@ -446,6 +451,9 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 
 		msq->q_qbytes = msqid64.msg_qbytes;
 
+		if (cmd == MSG_SET)
+			ipc_update_key(&msg_ids(ns), &msqid64.msg_perm, ipcp);
+
 		ipc_update_perm(&msqid64.msg_perm, ipcp);
 		msq->q_ctime = get_seconds();
 		/* sleeping receivers might be excluded by
@@ -565,6 +573,7 @@ SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 	}
 	case IPC_SET:
 	case IPC_RMID:
+	case MSG_SET:
 		err = msgctl_down(ns, msqid, cmd, buf, version);
 		return err;
 	default:
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 1728a5e..1428f8d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4849,6 +4849,7 @@ static int selinux_msg_queue_msgctl(struct msg_queue *msq, int cmd)
 		perms = MSGQ__GETATTR | MSGQ__ASSOCIATE;
 		break;
 	case IPC_SET:
+	case MSG_SET:
 		perms = MSGQ__SETATTR;
 		break;
 	case IPC_RMID:
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 4765659..143c053 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2450,6 +2450,7 @@ static int smack_msg_queue_msgctl(struct msg_queue *msq, int cmd)
 		may = MAY_READ;
 		break;
 	case IPC_SET:
+	case MSG_SET:
 	case IPC_RMID:
 		may = MAY_READWRITE;
 		break;