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fix idr_find() locking

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This is a patch that fixes the way idr_find() used to be called in ipc_lock():
in all the paths that don't imply an update of the ipcs idr, it was called
without the idr tree being locked.

The changes are:
  . in ipc_ids, the mutex has been changed into a reader/writer semaphore.
  . ipc_lock() now takes the mutex as a reader during the idr_find().
  . a new routine ipc_lock_down() has been defined: it doesn't take the
    mutex, assuming that it is being held by the caller. This is the routine
    that is now called in all the update paths.

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Acked-by: Jarek Poplawski <jarkao2@o2.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nadia Derbey
2007-10-18 23:40:54 -07:00
committed by Linus Torvalds
parent f4566f0485
commit 3e148c7993
5 changed files with 198 additions and 70 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
ipc/msg.c
View File

@@ -34,7 +34,7 @@
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <asm/current.h>
@@ -110,7 +110,7 @@ void msg_exit_ns(struct ipc_namespace *ns)
int next_id;
int total, in_use;
mutex_lock(&msg_ids(ns).mutex);
down_write(&msg_ids(ns).rw_mutex);
in_use = msg_ids(ns).in_use;
@@ -122,7 +122,8 @@ void msg_exit_ns(struct ipc_namespace *ns)
freeque(ns, msq);
total++;
}
mutex_unlock(&msg_ids(ns).mutex);
up_write(&msg_ids(ns).rw_mutex);
kfree(ns->ids[IPC_MSG_IDS]);
ns->ids[IPC_MSG_IDS] = NULL;
@@ -136,6 +137,22 @@ void __init msg_init(void)
IPC_MSG_IDS, sysvipc_msg_proc_show);
}
/*
* This routine is called in the paths where the rw_mutex is held to protect
* access to the idr tree.
*/
static inline struct msg_queue *msg_lock_check_down(struct ipc_namespace *ns,
int id)
{
struct kern_ipc_perm *ipcp = ipc_lock_check_down(&msg_ids(ns), id);
return container_of(ipcp, struct msg_queue, q_perm);
}
/*
* msg_lock_(check_) routines are called in the paths where the rw_mutex
* is not held.
*/
static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id)
{
struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id);
@@ -161,7 +178,7 @@ static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
* @ns: namespace
* @params: ptr to the structure that contains the key and msgflg
*
* Called with msg_ids.mutex held
* Called with msg_ids.rw_mutex held (writer)
*/
static int newque(struct ipc_namespace *ns, struct ipc_params *params)
{
@@ -260,8 +277,8 @@ static void expunge_all(struct msg_queue *msq, int res)
* removes the message queue from message queue ID IDR, and cleans up all the
* messages associated with this queue.
*
* msg_ids.mutex and the spinlock for this message queue are held
* before freeque() is called. msg_ids.mutex remains locked on exit.
* msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
* before freeque() is called. msg_ids.rw_mutex remains locked on exit.
*/
static void freeque(struct ipc_namespace *ns, struct msg_queue *msq)
{
@@ -286,7 +303,7 @@ static void freeque(struct ipc_namespace *ns, struct msg_queue *msq)
}
/*
* Called with msg_ids.mutex and ipcp locked.
* Called with msg_ids.rw_mutex and ipcp locked.
*/
static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
{
@@ -444,7 +461,7 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
msginfo.msgmnb = ns->msg_ctlmnb;
msginfo.msgssz = MSGSSZ;
msginfo.msgseg = MSGSEG;
mutex_lock(&msg_ids(ns).mutex);
down_read(&msg_ids(ns).rw_mutex);
if (cmd == MSG_INFO) {
msginfo.msgpool = msg_ids(ns).in_use;
msginfo.msgmap = atomic_read(&msg_hdrs);
@@ -455,7 +472,7 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
msginfo.msgtql = MSGTQL;
}
max_id = ipc_get_maxid(&msg_ids(ns));
mutex_unlock(&msg_ids(ns).mutex);
up_read(&msg_ids(ns).rw_mutex);
if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
return -EFAULT;
return (max_id < 0) ? 0 : max_id;
@@ -516,8 +533,8 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
return -EINVAL;
}
mutex_lock(&msg_ids(ns).mutex);
msq = msg_lock_check(ns, msqid);
down_write(&msg_ids(ns).rw_mutex);
msq = msg_lock_check_down(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_up;
@@ -576,7 +593,7 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
}
err = 0;
out_up:
mutex_unlock(&msg_ids(ns).mutex);
up_write(&msg_ids(ns).rw_mutex);
return err;
out_unlock_up:
msg_unlock(msq);