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authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-07-08 16:01:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-09 10:33:27 -0700
commit7b4cc5d8411bd4e9d61d8714f53859740cf830c2 (patch)
treeb95f3b875a5f4c927b0f27cc3c7ddcba5cc8e1e8 /ipc/shm.c
parentcf9d5d78d05bca96df7618dfc3a5ee4414dcae58 (diff)
downloadlinux-sh-7b4cc5d8411bd4e9d61d8714f53859740cf830c2.tar.gz
ipc: move locking out of ipcctl_pre_down_nolock
This function currently acquires both the rw_mutex and the rcu lock on successful lookups, leaving the callers to explicitly unlock them, creating another two level locking situation. Make the callers (including those that still use ipcctl_pre_down()) explicitly lock and unlock the rwsem and rcu lock. Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/shm.c')
-rw-r--r--ipc/shm.c23
1 files changed, 17 insertions, 6 deletions
diff --git a/ipc/shm.c b/ipc/shm.c
index e7d51072d1c7..c6b4ad5ce3b7 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -757,31 +757,42 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
return -EFAULT;
}
+ down_write(&shm_ids(ns).rw_mutex);
+ rcu_read_lock();
+
ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd,
&shmid64.shm_perm, 0);
- if (IS_ERR(ipcp))
- return PTR_ERR(ipcp);
+ if (IS_ERR(ipcp)) {
+ err = PTR_ERR(ipcp);
+ /* the ipc lock is not held upon failure */
+ goto out_unlock1;
+ }
shp = container_of(ipcp, struct shmid_kernel, shm_perm);
err = security_shm_shmctl(shp, cmd);
if (err)
- goto out_unlock;
+ goto out_unlock0;
+
switch (cmd) {
case IPC_RMID:
+ /* do_shm_rmid unlocks the ipc object and rcu */
do_shm_rmid(ns, ipcp);
goto out_up;
case IPC_SET:
err = ipc_update_perm(&shmid64.shm_perm, ipcp);
if (err)
- goto out_unlock;
+ goto out_unlock0;
shp->shm_ctim = get_seconds();
break;
default:
err = -EINVAL;
}
-out_unlock:
- shm_unlock(shp);
+
+out_unlock0:
+ ipc_unlock_object(&shp->shm_perm);
+out_unlock1:
+ rcu_read_unlock();
out_up:
up_write(&shm_ids(ns).rw_mutex);
return err;