Commit 8d4cc8b5 authored by Pierre Peiffer's avatar Pierre Peiffer Committed by Linus Torvalds

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: default avatarPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6ff37972
......@@ -616,9 +616,77 @@ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
}
}
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 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
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:
......
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