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Commit b9a53227 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Initialize msg/shm IPC objects before doing ipc_addid() 



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 e8577d1f:
"ipc/sem.c: fully initialize sem_array before making it visible") but we
clearly forgot about msg and shm.

Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3225031f

ipc/msg.c

+7 −7
Original line number Diff line number Diff line
@@ -137,13 +137,6 @@ 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;
@@ -153,6 +146,13 @@ 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();

ipc/shm.c

+7 −6
Original line number Diff line number Diff line
@@ -551,12 +551,6 @@ 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;
@@ -565,6 +559,13 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) 
	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);



	/*

ipc/util.c

+4 −4
Original line number Diff line number Diff line
@@ -237,6 +237,10 @@ 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);
@@ -249,10 +253,6 @@ 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 > IPCID_SEQ_MAX)