Patch "Initialize msg/shm IPC objects before doing ipc_addid()" has been added to the 4.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Initialize msg/shm IPC objects before doing ipc_addid()

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     initialize-msg-shm-ipc-objects-before-doing-ipc_addid.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From b9a532277938798b53178d5a66af6e2915cb27cf Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 30 Sep 2015 12:48:40 -0400
Subject: Initialize msg/shm IPC objects before doing ipc_addid()

From: Linus Torvalds <torvalds@linux-foundation.org>

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 ipc/msg.c  |   14 +++++++-------
 ipc/shm.c  |   13 +++++++------
 ipc/util.c |    8 ++++----
 3 files changed, 18 insertions(+), 17 deletions(-)

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -137,13 +137,6 @@ static int newque(struct ipc_namespace *
 		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;
@@ -153,6 +146,13 @@ static int newque(struct ipc_namespace *
 	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();
 
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -550,12 +550,6 @@ static int newseg(struct ipc_namespace *
 	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;
@@ -564,6 +558,13 @@ static int newseg(struct ipc_namespace *
 	shp->shm_nattch = 0;
 	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;
+	}
+
 	list_add(&shp->shm_clist, &current->sysvshm.shm_clist);
 
 	/*
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -237,6 +237,10 @@ int ipc_addid(struct ipc_ids *ids, struc
 	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);
@@ -249,10 +253,6 @@ int ipc_addid(struct ipc_ids *ids, struc
 
 	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 > IPCID_SEQ_MAX)


Patches currently in stable-queue which might be from torvalds@linux-foundation.org are

queue-4.1/x86-efi-fix-boot-crash-by-mapping-efi-memmap-entries-bottom-up-at-runtime-instead-of-top-down.patch
queue-4.1/mm-hugetlbfs-skip-shared-vmas-when-unmapping-private-pages-to-satisfy-a-fault.patch
queue-4.1/x86-kexec-fix-kexec-crash-in-syscall-kexec_file_load.patch
queue-4.1/lib-iommu-common.c-do-not-try-to-deref-a-null-iommu-lazy_flush-pointer-when-n-pool-hint.patch
queue-4.1/time-fix-timekeeping_freqadjust-s-incorrect-use-of-abs-instead-of-abs64.patch
queue-4.1/perf-x86-intel-fix-constraint-access.patch
queue-4.1/ocfs2-dlm-fix-deadlock-when-dispatch-assert-master.patch
queue-4.1/mm-migrate-hugetlb-putback-destination-hugepage-to-active-list.patch
queue-4.1/x86-mm-set-nx-on-gap-between-__ex_table-and-rodata.patch
queue-4.1/initialize-msg-shm-ipc-objects-before-doing-ipc_addid.patch
queue-4.1/sched-core-fix-task_dead-race-in-finish_task_switch.patch
queue-4.1/perf-fix-aux-buffer-refcounting.patch
queue-4.1/sched-fair-prevent-throttling-in-early-pick_next_task_fair.patch
queue-4.1/x86-platform-fix-geode-lx-timekeeping-in-the-generic-x86-build.patch