From ef177b34f44947335d283f8da4f4783b6a896830 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 11 Sep 2013 14:26:16 -0700 Subject: [PATCH] ipc,shm: shorten critical region in shmctl_down commit 79ccf0f8c8e04e8b9eda6645ba0f63b0915a3075 upstream. Instead of holding the ipc lock for the entire function, use the ipcctl_pre_down_nolock and only acquire the lock for specific commands: RMID and SET. Signed-off-by: Davidlohr Bueso Tested-by: Sedat Dilek Cc: Rik van Riel Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- ipc/shm.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index ce86e53d3175b..715f61fa5a16b 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -787,11 +787,10 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, down_write(&shm_ids(ns).rw_mutex); rcu_read_lock(); - ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd, - &shmid64.shm_perm, 0); + ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd, + &shmid64.shm_perm, 0); if (IS_ERR(ipcp)) { err = PTR_ERR(ipcp); - /* the ipc lock is not held upon failure */ goto out_unlock1; } @@ -799,14 +798,16 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, err = security_shm_shmctl(shp, cmd); if (err) - goto out_unlock0; + goto out_unlock1; switch (cmd) { case IPC_RMID: + ipc_lock_object(&shp->shm_perm); /* do_shm_rmid unlocks the ipc object and rcu */ do_shm_rmid(ns, ipcp); goto out_up; case IPC_SET: + ipc_lock_object(&shp->shm_perm); err = ipc_update_perm(&shmid64.shm_perm, ipcp); if (err) goto out_unlock0; @@ -814,6 +815,7 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, break; default: err = -EINVAL; + goto out_unlock1; } out_unlock0: -- 2.47.2