ipcctl_pre_down_nolock
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## Name

ipcctl_pre_down_nolock — retrieve an ipc and check permissions for some IPC_XXX cmd

## Synopsis

`struct kern_ipc_perm * ipcctl_pre_down_nolock (` | struct ipc_namespace * ns,
| struct ipc_ids * ids,
| int id,
| int cmd,
| struct ipc64_perm * perm,
| int extra_perm`)`;

## Arguments

`ns`

  the ipc namespace

`ids`

  the table of ids where to look for the ipc

`id`

  the id of the ipc to retrieve

`cmd`

  the cmd to check

`perm`

  the permission to set

`extra_perm`

  one extra permission parameter used by msq

## Description

This function does some common audit and permissions check for some IPC_XXX cmd and is called from semctl_down, shmctl_down and msgctl_down. It must be called without any lock held and - retrieves the ipc with the given id in the given table. - performs some audit and permission check, depending on the given cmd - returns a pointer to the ipc object or otherwise, the corresponding error.

Call holding the both the rwsem and the rcu read lock.

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