From c97cb9ccab8c85428ec21eff690642ad2ce1fa8a Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 11 Sep 2013 14:26:20 -0700 Subject: ipc,shm: make shmctl_nolock lockless While the INFO cmd doesn't take the ipc lock, the STAT commands do acquire it unnecessarily. We can do the permissions and security checks only holding the rcu lock. [akpm@linux-foundation.org: coding-style fixes] 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 --- ipc/shm.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'ipc/shm.c') diff --git a/ipc/shm.c b/ipc/shm.c index 3e123987f054..a493639550d9 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -882,27 +882,31 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, struct shmid64_ds tbuf; int result; + rcu_read_lock(); if (cmd == SHM_STAT) { - shp = shm_lock(ns, shmid); + shp = shm_obtain_object(ns, shmid); if (IS_ERR(shp)) { err = PTR_ERR(shp); - goto out; + goto out_unlock; } result = shp->shm_perm.id; } else { - shp = shm_lock_check(ns, shmid); + shp = shm_obtain_object_check(ns, shmid); if (IS_ERR(shp)) { err = PTR_ERR(shp); - goto out; + goto out_unlock; } result = 0; } + err = -EACCES; if (ipcperms(ns, &shp->shm_perm, S_IRUGO)) goto out_unlock; + err = security_shm_shmctl(shp, cmd); if (err) goto out_unlock; + memset(&tbuf, 0, sizeof(tbuf)); kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm); tbuf.shm_segsz = shp->shm_segsz; @@ -912,8 +916,9 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, tbuf.shm_cpid = shp->shm_cprid; tbuf.shm_lpid = shp->shm_lprid; tbuf.shm_nattch = shp->shm_nattch; - shm_unlock(shp); - if(copy_shmid_to_user (buf, &tbuf, version)) + rcu_read_unlock(); + + if (copy_shmid_to_user(buf, &tbuf, version)) err = -EFAULT; else err = result; @@ -924,7 +929,7 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, } out_unlock: - shm_unlock(shp); + rcu_read_unlock(); out: return err; } -- cgit v1.2.3