ipc,shm: shorten critical region for shmat
Similar to other system calls, acquire the kern_ipc_perm lock after doing
the initial permission and security checks.
[[email protected]: dont leave do_shmat with rcu lock held]
Signed-off-by: Davidlohr Bueso <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Manfred Spraul <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/ipc/shm.c b/ipc/shm.c
index 115dcce..28d19f4 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -19,6 +19,9 @@
* namespaces support
* OpenVZ, SWsoft Inc.
* Pavel Emelianov <[email protected]>
+ *
+ * Better ipc lock (kern_ipc_perm.lock) handling
+ * Davidlohr Bueso <[email protected]>, June 2013.
*/
#include <linux/slab.h>
@@ -1086,10 +1089,11 @@
* additional creator id...
*/
ns = current->nsproxy->ipc_ns;
- shp = shm_lock_check(ns, shmid);
+ rcu_read_lock();
+ shp = shm_obtain_object_check(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
- goto out;
+ goto out_unlock;
}
err = -EACCES;
@@ -1100,11 +1104,13 @@
if (err)
goto out_unlock;
+ ipc_lock_object(&shp->shm_perm);
path = shp->shm_file->f_path;
path_get(&path);
shp->shm_nattch++;
size = i_size_read(path.dentry->d_inode);
- shm_unlock(shp);
+ ipc_unlock_object(&shp->shm_perm);
+ rcu_read_unlock();
err = -ENOMEM;
sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
@@ -1175,7 +1181,7 @@
return err;
out_unlock:
- shm_unlock(shp);
+ rcu_read_unlock();
out:
return err;
}
