IPC/shared memory: introduce shmctl_down
Currently, the way the different commands are handled in sys_shmctl introduces
some duplicated code.
This patch introduces the shmctl_down function to handle all the commands
requiring the rwmutex to be taken in write mode (ie IPC_SET and IPC_RMID for
now). It is the equivalent function of semctl_down for shared memory.
This removes some duplicated code for handling these both commands and
harmonizes the way they are handled among all IPCs.
Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/shm.c b/ipc/shm.c
index 3e4aff9..65a44bc 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -616,10 +616,78 @@
}
}
-asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
+/*
+ * This function handles some shmctl commands which require the rw_mutex
+ * to be held in write mode.
+ * NOTE: no locks must be held, the rw_mutex is taken inside this function.
+ */
+static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
+ struct shmid_ds __user *buf, int version)
{
+ struct kern_ipc_perm *ipcp;
struct shm_setbuf setbuf;
struct shmid_kernel *shp;
+ int err;
+
+ if (cmd == IPC_SET) {
+ if (copy_shmid_from_user(&setbuf, buf, version))
+ return -EFAULT;
+ }
+
+ down_write(&shm_ids(ns).rw_mutex);
+ shp = shm_lock_check_down(ns, shmid);
+ if (IS_ERR(shp)) {
+ err = PTR_ERR(shp);
+ goto out_up;
+ }
+
+ ipcp = &shp->shm_perm;
+
+ err = audit_ipc_obj(ipcp);
+ if (err)
+ goto out_unlock;
+
+ if (cmd == IPC_SET) {
+ err = audit_ipc_set_perm(0, setbuf.uid,
+ setbuf.gid, setbuf.mode);
+ if (err)
+ goto out_unlock;
+ }
+
+ if (current->euid != ipcp->uid &&
+ current->euid != ipcp->cuid &&
+ !capable(CAP_SYS_ADMIN)) {
+ err = -EPERM;
+ goto out_unlock;
+ }
+
+ err = security_shm_shmctl(shp, cmd);
+ if (err)
+ goto out_unlock;
+ switch (cmd) {
+ case IPC_RMID:
+ do_shm_rmid(ns, ipcp);
+ goto out_up;
+ case IPC_SET:
+ ipcp->uid = setbuf.uid;
+ ipcp->gid = setbuf.gid;
+ ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
+ | (setbuf.mode & S_IRWXUGO);
+ shp->shm_ctim = get_seconds();
+ break;
+ default:
+ err = -EINVAL;
+ }
+out_unlock:
+ shm_unlock(shp);
+out_up:
+ up_write(&shm_ids(ns).rw_mutex);
+ return err;
+}
+
+asmlinkage long sys_shmctl(int shmid, int cmd, struct shmid_ds __user *buf)
+{
+ struct shmid_kernel *shp;
int err, version;
struct ipc_namespace *ns;
@@ -775,97 +843,13 @@
goto out;
}
case IPC_RMID:
- {
- /*
- * We cannot simply remove the file. The SVID states
- * that the block remains until the last person
- * detaches from it, then is deleted. A shmat() on
- * an RMID segment is legal in older Linux and if
- * we change it apps break...
- *
- * Instead we set a destroyed flag, and then blow
- * the name away when the usage hits zero.
- */
- down_write(&shm_ids(ns).rw_mutex);
- shp = shm_lock_check_down(ns, shmid);
- if (IS_ERR(shp)) {
- err = PTR_ERR(shp);
- goto out_up;
- }
-
- err = audit_ipc_obj(&(shp->shm_perm));
- if (err)
- goto out_unlock_up;
-
- if (current->euid != shp->shm_perm.uid &&
- current->euid != shp->shm_perm.cuid &&
- !capable(CAP_SYS_ADMIN)) {
- err=-EPERM;
- goto out_unlock_up;
- }
-
- err = security_shm_shmctl(shp, cmd);
- if (err)
- goto out_unlock_up;
-
- do_shm_rmid(ns, &shp->shm_perm);
- up_write(&shm_ids(ns).rw_mutex);
- goto out;
- }
-
case IPC_SET:
- {
- if (!buf) {
- err = -EFAULT;
- goto out;
- }
-
- if (copy_shmid_from_user (&setbuf, buf, version)) {
- err = -EFAULT;
- goto out;
- }
- down_write(&shm_ids(ns).rw_mutex);
- shp = shm_lock_check_down(ns, shmid);
- if (IS_ERR(shp)) {
- err = PTR_ERR(shp);
- goto out_up;
- }
- err = audit_ipc_obj(&(shp->shm_perm));
- if (err)
- goto out_unlock_up;
- err = audit_ipc_set_perm(0, setbuf.uid, setbuf.gid, setbuf.mode);
- if (err)
- goto out_unlock_up;
- err=-EPERM;
- if (current->euid != shp->shm_perm.uid &&
- current->euid != shp->shm_perm.cuid &&
- !capable(CAP_SYS_ADMIN)) {
- goto out_unlock_up;
- }
-
- err = security_shm_shmctl(shp, cmd);
- if (err)
- goto out_unlock_up;
-
- shp->shm_perm.uid = setbuf.uid;
- shp->shm_perm.gid = setbuf.gid;
- shp->shm_perm.mode = (shp->shm_perm.mode & ~S_IRWXUGO)
- | (setbuf.mode & S_IRWXUGO);
- shp->shm_ctim = get_seconds();
- break;
- }
-
+ err = shmctl_down(ns, shmid, cmd, buf, version);
+ return err;
default:
- err = -EINVAL;
- goto out;
+ return -EINVAL;
}
- err = 0;
-out_unlock_up:
- shm_unlock(shp);
-out_up:
- up_write(&shm_ids(ns).rw_mutex);
- goto out;
out_unlock:
shm_unlock(shp);
out:
