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Subject[ 51/69] ipc,shm: introduce shmctl_nolock
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davidlohr Bueso <davidlohr.bueso@hp.com>

commit 68eccc1dc345539d589ae78ee43b835c1a06a134 upstream.

Similar to semctl and msgctl, when calling msgctl, the *_INFO and *_STAT
commands can be performed without acquiring the ipc object.

Add a shmctl_nolock() function and move the logic of *_INFO and *_STAT out
of msgctl(). Since we are just moving functionality, this change still
takes the lock and it will be properly lockless in the next patch.

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>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
ipc/shm.c | 57 +++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 39 insertions(+), 18 deletions(-)

--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -820,29 +820,24 @@ out_up:
return err;
}

-SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
+ int cmd, int version, void __user *buf)
{
+ int err;
struct shmid_kernel *shp;
- int err, version;
- struct ipc_namespace *ns;

- if (cmd < 0 || shmid < 0) {
- err = -EINVAL;
- goto out;
+ /* preliminary security checks for *_INFO */
+ if (cmd == IPC_INFO || cmd == SHM_INFO) {
+ err = security_shm_shmctl(NULL, cmd);
+ if (err)
+ return err;
}

- version = ipc_parse_version(&cmd);
- ns = current->nsproxy->ipc_ns;
-
- switch (cmd) { /* replace with proc interface ? */
+ switch (cmd) {
case IPC_INFO:
{
struct shminfo64 shminfo;

- err = security_shm_shmctl(NULL, cmd);
- if (err)
- return err;
-
memset(&shminfo, 0, sizeof(shminfo));
shminfo.shmmni = shminfo.shmseg = ns->shm_ctlmni;
shminfo.shmmax = ns->shm_ctlmax;
@@ -864,10 +859,6 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
{
struct shm_info shm_info;

- err = security_shm_shmctl(NULL, cmd);
- if (err)
- return err;
-
memset(&shm_info, 0, sizeof(shm_info));
down_read(&shm_ids(ns).rw_mutex);
shm_info.used_ids = shm_ids(ns).in_use;
@@ -928,6 +919,36 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
err = result;
goto out;
}
+ default:
+ return -EINVAL;
+ }
+
+out_unlock:
+ shm_unlock(shp);
+out:
+ return err;
+}
+
+SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+{
+ struct shmid_kernel *shp;
+ int err, version;
+ struct ipc_namespace *ns;
+
+ if (cmd < 0 || shmid < 0) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ version = ipc_parse_version(&cmd);
+ ns = current->nsproxy->ipc_ns;
+
+ switch (cmd) {
+ case IPC_INFO:
+ case SHM_INFO:
+ case SHM_STAT:
+ case IPC_STAT:
+ return shmctl_nolock(ns, shmid, cmd, version, buf);
case SHM_LOCK:
case SHM_UNLOCK:
{



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