From a845bb16c8374e66fbc33ddbc39d87c7048497f1 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 30 Sep 2015 12:48:40 -0400 Subject: [PATCH] Initialize msg/shm IPC objects before doing ipc_addid() (cherry pick from commit b9a532277938798b53178d5a66af6e2915cb27cf) 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 Cc: Manfred Spraul Cc: Davidlohr Bueso Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Mark Salyzyn Bug: 24551430 Change-Id: Ic7b980a6f2a79eb3c04fc43b6531c396645af1db --- ipc/msg.c | 17 ++++++++--------- ipc/shm.c | 12 ++++++------ ipc/util.c | 8 ++++---- 3 files changed, 18 insertions(+), 19 deletions(-) diff --git a/ipc/msg.c b/ipc/msg.c index f450cd4b..bcf96720 100644 --- 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; @@ -218,8 +211,14 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params) INIT_LIST_HEAD(&msq->q_receivers); INIT_LIST_HEAD(&msq->q_senders); - ipc_unlock_object(&msq->q_perm); - rcu_read_unlock(); + /* 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; + } + + msg_unlock(msq); return msq->q_perm.id; } diff --git a/ipc/shm.c b/ipc/shm.c index b7b1f765..c20279ae 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -554,12 +554,6 @@ 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; @@ -569,6 +563,12 @@ 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 7684f41b..73534257 100644 --- 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)