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ipc: move locking out of ipcctl_pre_down_nolock

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This function currently acquires both the rw_mutex and the rcu lock on
successful lookups, leaving the callers to explicitly unlock them,
creating another two level locking situation.

Make the callers (including those that still use ipcctl_pre_down())
explicitly lock and unlock the rwsem and rcu lock.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso
2013-07-08 16:01:12 -07:00
committed by Linus Torvalds
parent cf9d5d78d0
commit 7b4cc5d841
4 changed files with 56 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files
ipc/util.c
+6 -15
View File
@@ -746,8 +746,10 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
* 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 the ipc with both ipc and rw_mutex locks held in case of success
* - returns the ipc with the ipc lock held in case of success
* or an err-code without any lock held otherwise.
*
* Call holding the both the rw_mutex and the rcu read lock.
*/
struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
struct ipc_ids *ids, int id, int cmd,
@@ -772,13 +774,10 @@ struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
int err = -EPERM;
struct kern_ipc_perm *ipcp;
down_write(&ids->rw_mutex);
rcu_read_lock();
ipcp = ipc_obtain_object_check(ids, id);
if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp);
goto out_up;
goto err;
}
audit_ipc_obj(ipcp);
@@ -789,16 +788,8 @@ struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
euid = current_euid();
if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid) ||
ns_capable(ns->user_ns, CAP_SYS_ADMIN))
return ipcp;
out_up:
/*
* Unsuccessful lookup, unlock and return
* the corresponding error.
*/
rcu_read_unlock();
up_write(&ids->rw_mutex);
return ipcp; /* successful lookup */
err:
return ERR_PTR(err);
}