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| author | Davidlohr Bueso <davidlohr.bueso@hp.com> | 2013-07-08 16:01:12 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-10-18 07:45:46 -0700 |
| commit | ac9bc6e396285ab732dd869c3edb353662134022 (patch) | |
| tree | 182b0be2e0238d96e02c8669e372c254d6ea81a1 /ipc/shm.c | |
| parent | 115d40dbef93b70e6f32732b0fdd5903c1f7fce4 (diff) | |
| download | linux-3.10-ac9bc6e396285ab732dd869c3edb353662134022.tar.gz linux-3.10-ac9bc6e396285ab732dd869c3edb353662134022.tar.bz2 linux-3.10-ac9bc6e396285ab732dd869c3edb353662134022.zip | |
ipc: move locking out of ipcctl_pre_down_nolock
commit 7b4cc5d8411bd4e9d61d8714f53859740cf830c2 upstream.
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>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'ipc/shm.c')
| -rw-r--r-- | ipc/shm.c | 23 |
1 files changed, 17 insertions, 6 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index 25471fd9f31..cc6ee982ea0 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; |