diff options
| author | Davidlohr Bueso <davidlohr.bueso@hp.com> | 2013-09-11 14:26:20 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-11 15:59:39 -0700 |
| commit | c97cb9ccab8c85428ec21eff690642ad2ce1fa8a (patch) | |
| tree | c435476a079d3bff28ec8c67377227effba57ca9 /ipc | |
| parent | 68eccc1dc345539d589ae78ee43b835c1a06a134 (diff) | |
| download | lwn-c97cb9ccab8c85428ec21eff690642ad2ce1fa8a.tar.gz lwn-c97cb9ccab8c85428ec21eff690642ad2ce1fa8a.zip | |
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 <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/shm.c | 19 |
1 files changed, 12 insertions, 7 deletions
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; } |