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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 <[email protected]>
Acked-by: Jarek Poplawski <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Nadia Derbey 2007-10-18 23:40:54 -07:00 • committed by Linus Torvalds
commit 3e148c7993
5 changed files with 198 additions and 70 deletions
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44
ipc/sem.c
View file

@ -80,7 +80,7 @@
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <asm/uaccess.h>
@ -148,7 +148,7 @@ void sem_exit_ns(struct ipc_namespace *ns)
int next_id;
int total, in_use;
mutex_lock(&sem_ids(ns).mutex);
down_write(&sem_ids(ns).rw_mutex);
in_use = sem_ids(ns).in_use;
@ -160,7 +160,7 @@ void sem_exit_ns(struct ipc_namespace *ns)
freeary(ns, sma);
total++;
}
mutex_unlock(&sem_ids(ns).mutex);
up_write(&sem_ids(ns).rw_mutex);
kfree(ns->ids[IPC_SEM_IDS]);
ns->ids[IPC_SEM_IDS] = NULL;
@ -174,6 +174,22 @@ void __init sem_init (void)
IPC_SEM_IDS, sysvipc_sem_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 sem_array *sem_lock_check_down(struct ipc_namespace *ns,
int id)
{
struct kern_ipc_perm *ipcp = ipc_lock_check_down(&sem_ids(ns), id);
return container_of(ipcp, struct sem_array, sem_perm);
}
/*
* sem_lock_(check_) routines are called in the paths where the rw_mutex
* is not held.
*/
static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
{
struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
@ -233,7 +249,7 @@ static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
* @ns: namespace
* @params: ptr to the structure that contains key, semflg and nsems
*
* Called with sem_ids.mutex held
* Called with sem_ids.rw_mutex held (as a writer)
*/
static int newary(struct ipc_namespace *ns, struct ipc_params *params)
@ -290,7 +306,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
/*
* Called with sem_ids.mutex and ipcp locked.
* Called with sem_ids.rw_mutex and ipcp locked.
*/
static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
{
@ -301,7 +317,7 @@ static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
}
/*
* Called with sem_ids.mutex and ipcp locked.
* Called with sem_ids.rw_mutex and ipcp locked.
*/
static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
struct ipc_params *params)
@ -528,9 +544,9 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
return semzcnt;
}
/* Free a semaphore set. freeary() is called with sem_ids.mutex locked and
* the spinlock for this semaphore set hold. sem_ids.mutex remains locked
* on exit.
/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
* as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
* remains locked on exit.
*/
static void freeary(struct ipc_namespace *ns, struct sem_array *sma)
{
@ -615,7 +631,7 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
seminfo.semmnu = SEMMNU;
seminfo.semmap = SEMMAP;
seminfo.semume = SEMUME;
mutex_lock(&sem_ids(ns).mutex);
down_read(&sem_ids(ns).rw_mutex);
if (cmd == SEM_INFO) {
seminfo.semusz = sem_ids(ns).in_use;
seminfo.semaem = ns->used_sems;
@ -624,7 +640,7 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
seminfo.semaem = SEMAEM;
}
max_id = ipc_get_maxid(&sem_ids(ns));
mutex_unlock(&sem_ids(ns).mutex);
up_read(&sem_ids(ns).rw_mutex);
if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
return -EFAULT;
return (max_id < 0) ? 0: max_id;
@ -895,7 +911,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
if(copy_semid_from_user (&setbuf, arg.buf, version))
return -EFAULT;
}
sma = sem_lock_check(ns, semid);
sma = sem_lock_check_down(ns, semid);
if (IS_ERR(sma))
return PTR_ERR(sma);
@ -976,9 +992,9 @@ asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
return err;
case IPC_RMID:
case IPC_SET:
mutex_lock(&sem_ids(ns).mutex);
down_write(&sem_ids(ns).rw_mutex);
err = semctl_down(ns,semid,semnum,cmd,version,arg);
mutex_unlock(&sem_ids(ns).mutex);
up_write(&sem_ids(ns).rw_mutex);
return err;
default:
return -EINVAL;