Initialize msg/shm IPC objects before doing ipc_addid()

commit b9a532277938798b53178d5a66af6e2915cb27cf upstream.

As reported by Dmitry Vyukov, we really shouldn't do ipc_addid() before
having initialized the IPC object state.  Yes, we initialize the IPC
object in a locked state, but with all the lockless RCU lookup work,
that IPC object lock no longer means that the state cannot be seen.

We already did this for the IPC semaphore code (see commit e8577d1f0329:
"ipc/sem.c: fully initialize sem_array before making it visible") but we
clearly forgot about msg and shm.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/ipc/msg.c b/ipc/msg.c
index 52770bfde2a5afe9eaf2f9694ed4a74250ac89c1..32aaaab15c5c46ae12c90d58693df7a0bb47d9b8 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -202,13 +202,6 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
                return retval;
        }
 
-       /* ipc_addid() locks msq upon success. */
-       id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
-       if (id < 0) {
-               ipc_rcu_putref(msq, msg_rcu_free);
-               return id;
-       }
-
        msq->q_stime = msq->q_rtime = 0;
        msq->q_ctime = get_seconds();
        msq->q_cbytes = msq->q_qnum = 0;
@@ -218,6 +211,13 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
        INIT_LIST_HEAD(&msq->q_receivers);
        INIT_LIST_HEAD(&msq->q_senders);
 
+       /* ipc_addid() locks msq upon success. */
+       id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
+       if (id < 0) {
+               ipc_rcu_putref(msq, msg_rcu_free);
+               return id;
+       }
+
        ipc_unlock_object(&msq->q_perm);
        rcu_read_unlock();
 

diff --git a/ipc/shm.c b/ipc/shm.c
index 623bc3877118f1c940d143f3f8dd65da14374017..02f7125c8a0fbca545a5ce2e3459008656851f4b 100644 (file)
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -545,12 +545,6 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
        if (IS_ERR(file))
                goto no_file;
 
-       id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
-       if (id < 0) {
-               error = id;
-               goto no_id;
-       }
-
        shp->shm_cprid = task_tgid_vnr(current);
        shp->shm_lprid = 0;
        shp->shm_atim = shp->shm_dtim = 0;
@@ -560,6 +554,12 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
        shp->shm_file = file;
        shp->shm_creator = current;
 
+       id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
+       if (id < 0) {
+               error = id;
+               goto no_id;
+       }
+
        /*
         * shmid gets reported as "inode#" in /proc/pid/maps.
         * proc-ps tools use this. Changing this will break them.

diff --git a/ipc/util.c b/ipc/util.c
index 7684f41bce76a9b430f04b7e4e77810b48798a42..735342570a875fea7eb77029c1db2fcbc797d422 100644 (file)
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -292,6 +292,10 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
        rcu_read_lock();
        spin_lock(&new->lock);
 
+       current_euid_egid(&euid, &egid);
+       new->cuid = new->uid = euid;
+       new->gid = new->cgid = egid;
+
        id = idr_alloc(&ids->ipcs_idr, new,
                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
                       GFP_NOWAIT);
@@ -304,10 +308,6 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 
        ids->in_use++;
 
-       current_euid_egid(&euid, &egid);
-       new->cuid = new->uid = euid;
-       new->gid = new->cgid = egid;
-
        if (next_id < 0) {
                new->seq = ids->seq++;
                if (ids->seq > ids->seq_max)