1 files changed, 30 insertions, 14 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 558aa91186b6..245db1140ad6 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -253,8 +253,14 @@ static void expunge_all(struct msg_queue *msq, int res)
         struct msg_receiver *msr, *t;
 
         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
-                msr->r_msg = NULL;
+                msr->r_msg = NULL; /* initialize expunge ordering */
                 wake_up_process(msr->r_tsk);
+                /*
+                 * Ensure that the wakeup is visible before setting r_msg as
+                 * the receiving end depends on it: either spinning on a nil,
+                 * or dealing with -EAGAIN cases. See lockless receive part 1
+                 * and 2 in do_msgrcv().
+                 */
                 smp_mb();
                 msr->r_msg = ERR_PTR(res);
         }
@@ -318,7 +324,7 @@ SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 static inline unsigned long
 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 {
-        switch(version) {
+        switch (version) {
         case IPC_64:
                 return copy_to_user(buf, in, sizeof(*in));
         case IPC_OLD:
@@ -363,7 +369,7 @@ copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 static inline unsigned long
 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 {
-        switch(version) {
+        switch (version) {
         case IPC_64:
                 if (copy_from_user(out, buf, sizeof(*out)))
                         return -EFAULT;
@@ -375,9 +381,9 @@ copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
                         return -EFAULT;
 
-                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.uid       = tbuf_old.msg_perm.uid;
+                out->msg_perm.gid       = tbuf_old.msg_perm.gid;
+                out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 
                 if (tbuf_old.msg_qbytes == 0)
                         out->msg_qbytes = tbuf_old.msg_lqbytes;
@@ -606,13 +612,13 @@ SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 
 static int testmsg(struct msg_msg *msg, long type, int mode)
 {
-        switch(mode)
+        switch (mode)
         {
                 case SEARCH_ANY:
                 case SEARCH_NUMBER:
                         return 1;
                 case SEARCH_LESSEQUAL:
-                        if (msg->m_type <=type)
+                        if (msg->m_type <= type)
                                 return 1;
                         break;
                 case SEARCH_EQUAL:
@@ -638,15 +644,22 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 
                         list_del(&msr->r_list);
                         if (msr->r_maxsize < msg->m_ts) {
+                                /* initialize pipelined send ordering */
                                 msr->r_msg = NULL;
                                 wake_up_process(msr->r_tsk);
-                                smp_mb();
+                                smp_mb(); /* see barrier comment below */
                                 msr->r_msg = ERR_PTR(-E2BIG);
                         } else {
                                 msr->r_msg = NULL;
                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
                                 msq->q_rtime = get_seconds();
                                 wake_up_process(msr->r_tsk);
+                                /*
+                                 * Ensure that the wakeup is visible before
+                                 * setting r_msg, as the receiving end depends
+                                 * on it. See lockless receive part 1 and 2 in
+                                 * do_msgrcv().
+                                 */
                                 smp_mb();
                                 msr->r_msg = msg;
 
@@ -654,6 +667,7 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
                         }
                 }
         }
+
         return 0;
 }
 
@@ -696,7 +710,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
                         goto out_unlock0;
 
                 /* raced with RMID? */
-                if (msq->q_perm.deleted) {
+                if (!ipc_valid_object(&msq->q_perm)) {
                         err = -EIDRM;
                         goto out_unlock0;
                 }
@@ -716,6 +730,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
                         goto out_unlock0;
                 }
 
+                /* enqueue the sender and prepare to block */
                 ss_add(msq, &s);
 
                 if (!ipc_rcu_getref(msq)) {
@@ -731,7 +746,8 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
                 ipc_lock_object(&msq->q_perm);
 
                 ipc_rcu_putref(msq, ipc_rcu_free);
-                if (msq->q_perm.deleted) {
+                /* raced with RMID? */
+                if (!ipc_valid_object(&msq->q_perm)) {
                         err = -EIDRM;
                         goto out_unlock0;
                 }
@@ -909,7 +925,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
                 ipc_lock_object(&msq->q_perm);
 
                 /* raced with RMID? */
-                if (msq->q_perm.deleted) {
+                if (!ipc_valid_object(&msq->q_perm)) {
                         msg = ERR_PTR(-EIDRM);
                         goto out_unlock0;
                 }
@@ -983,7 +999,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
                  * wake_up_process(). There is a race with exit(), see
                  * ipc/mqueue.c for the details.
                  */
-                msg = (struct msg_msg*)msr_d.r_msg;
+                msg = (struct msg_msg *)msr_d.r_msg;
                 while (msg == NULL) {
                         cpu_relax();
                         msg = (struct msg_msg *)msr_d.r_msg;
@@ -1004,7 +1020,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
                 /* Lockless receive, part 4:
                  * Repeat test after acquiring the spinlock.
                  */
-                msg = (struct msg_msg*)msr_d.r_msg;
+                msg = (struct msg_msg *)msr_d.r_msg;
                 if (msg != ERR_PTR(-EAGAIN))
                         goto out_unlock0;