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Commit 3e148c79 authored by Nadia Derbey's avatar Nadia Derbey Committed by Linus Torvalds
Browse files

fix idr_find() locking 



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: default avatarNadia Derbey <Nadia.Derbey@bull.net>
Acked-by: default avatarJarek Poplawski <jarkao2@o2.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f4566f04

ipc/msg.c

+29 −12
Original line number Diff line number Diff line
@@ -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);

ipc/sem.c

+30 −14
Original line number Diff line number Diff line
@@ -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;

ipc/shm.c

+51 −26
Original line number Diff line number Diff line
@@ -35,7 +35,7 @@ 
#include <linux/capability.h>

#include <linux/ptrace.h>

#include <linux/seq_file.h>

#include <linux/mutex.h>

#include <linux/rwsem.h>

#include <linux/nsproxy.h>

#include <linux/mount.h>
@@ -83,8 +83,8 @@ static void __shm_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids) 
}



/*

 * Called with shm_ids.mutex and the shp structure locked.

 * Only shm_ids.mutex remains locked on exit.

 * Called with shm_ids.rw_mutex (writer) and the shp structure locked.

 * Only shm_ids.rw_mutex remains locked on exit.

 */

static void do_shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *shp)

{
@@ -115,7 +115,7 @@ void shm_exit_ns(struct ipc_namespace *ns) 
	int next_id;

	int total, in_use;



	mutex_lock(&shm_ids(ns).mutex);

	down_write(&shm_ids(ns).rw_mutex);



	in_use = shm_ids(ns).in_use;
@@ -127,7 +127,7 @@ void shm_exit_ns(struct ipc_namespace *ns) 
		do_shm_rmid(ns, shp);

		total++;

	}

	mutex_unlock(&shm_ids(ns).mutex);

	up_write(&shm_ids(ns).rw_mutex);



	kfree(ns->ids[IPC_SHM_IDS]);

	ns->ids[IPC_SHM_IDS] = NULL;
@@ -141,6 +141,31 @@ void __init shm_init (void) 
				IPC_SHM_IDS, sysvipc_shm_proc_show);

}



/*

 * shm_lock_(check_)down routines are called in the paths where the rw_mutex

 * is held to protect access to the idr tree.

 */

static inline struct shmid_kernel *shm_lock_down(struct ipc_namespace *ns,

						int id)

{

	struct kern_ipc_perm *ipcp = ipc_lock_down(&shm_ids(ns), id);



	return container_of(ipcp, struct shmid_kernel, shm_perm);

}



static inline struct shmid_kernel *shm_lock_check_down(

						struct ipc_namespace *ns,

						int id)

{

	struct kern_ipc_perm *ipcp = ipc_lock_check_down(&shm_ids(ns), id);



	return container_of(ipcp, struct shmid_kernel, shm_perm);

}



/*

 * shm_lock_(check_) routines are called in the paths where the rw_mutex

 * is not held.

 */

static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)

{

	struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
@@ -189,7 +214,7 @@ static void shm_open(struct vm_area_struct *vma) 
 * @ns: namespace

 * @shp: struct to free

 *

 * It has to be called with shp and shm_ids.mutex locked,

 * It has to be called with shp and shm_ids.rw_mutex (writer) locked,

 * but returns with shp unlocked and freed.

 */

static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
@@ -220,9 +245,9 @@ static void shm_close(struct vm_area_struct *vma) 
	struct shmid_kernel *shp;

	struct ipc_namespace *ns = sfd->ns;



	mutex_lock(&shm_ids(ns).mutex);

	down_write(&shm_ids(ns).rw_mutex);

	/* remove from the list of attaches of the shm segment */

	shp = shm_lock(ns, sfd->id);

	shp = shm_lock_down(ns, sfd->id);

	BUG_ON(IS_ERR(shp));

	shp->shm_lprid = task_tgid_vnr(current);

	shp->shm_dtim = get_seconds();
@@ -232,7 +257,7 @@ static void shm_close(struct vm_area_struct *vma) 
		shm_destroy(ns, shp);

	else

		shm_unlock(shp);

	mutex_unlock(&shm_ids(ns).mutex);

	up_write(&shm_ids(ns).rw_mutex);

}



static int shm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
@@ -353,7 +378,7 @@ static struct vm_operations_struct shm_vm_ops = { 
 * @ns: namespace

 * @params: ptr to the structure that contains key, size and shmflg

 *

 * Called with shm_ids.mutex held

 * Called with shm_ids.rw_mutex held as a writer.

 */



static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
@@ -442,7 +467,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) 
}



/*

 * Called with shm_ids.mutex and ipcp locked.

 * Called with shm_ids.rw_mutex and ipcp locked.

 */

static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg)

{
@@ -453,7 +478,7 @@ static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg) 
}



/*

 * Called with shm_ids.mutex and ipcp locked.

 * Called with shm_ids.rw_mutex and ipcp locked.

 */

static inline int shm_more_checks(struct kern_ipc_perm *ipcp,

				struct ipc_params *params)
@@ -578,7 +603,7 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf 
}



/*

 * Called with shm_ids.mutex held

 * Called with shm_ids.rw_mutex held as a reader

 */

static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,

		unsigned long *swp)
@@ -649,9 +674,9 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
		if(copy_shminfo_to_user (buf, &shminfo, version))

			return -EFAULT;



		mutex_lock(&shm_ids(ns).mutex);

		down_read(&shm_ids(ns).rw_mutex);

		err = ipc_get_maxid(&shm_ids(ns));

		mutex_unlock(&shm_ids(ns).mutex);

		up_read(&shm_ids(ns).rw_mutex);



		if(err<0)

			err = 0;
@@ -666,14 +691,14 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
			return err;



		memset(&shm_info,0,sizeof(shm_info));

		mutex_lock(&shm_ids(ns).mutex);

		down_read(&shm_ids(ns).rw_mutex);

		shm_info.used_ids = shm_ids(ns).in_use;

		shm_get_stat (ns, &shm_info.shm_rss, &shm_info.shm_swp);

		shm_info.shm_tot = ns->shm_tot;

		shm_info.swap_attempts = 0;

		shm_info.swap_successes = 0;

		err = ipc_get_maxid(&shm_ids(ns));

		mutex_unlock(&shm_ids(ns).mutex);

		up_read(&shm_ids(ns).rw_mutex);

		if(copy_to_user (buf, &shm_info, sizeof(shm_info))) {

			err = -EFAULT;

			goto out;
@@ -786,8 +811,8 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
		 *	Instead we set a destroyed flag, and then blow

		 *	the name away when the usage hits zero.

		 */

		mutex_lock(&shm_ids(ns).mutex);

		shp = shm_lock_check(ns, shmid);

		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;
@@ -809,7 +834,7 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
			goto out_unlock_up;



		do_shm_rmid(ns, shp);

		mutex_unlock(&shm_ids(ns).mutex);

		up_write(&shm_ids(ns).rw_mutex);

		goto out;

	}
@@ -824,8 +849,8 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
			err = -EFAULT;

			goto out;

		}

		mutex_lock(&shm_ids(ns).mutex);

		shp = shm_lock_check(ns, shmid);

		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;
@@ -864,7 +889,7 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) 
out_unlock_up:

	shm_unlock(shp);

out_up:

	mutex_unlock(&shm_ids(ns).mutex);

	up_write(&shm_ids(ns).rw_mutex);

	goto out;

out_unlock:

	shm_unlock(shp);
@@ -998,8 +1023,8 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr) 
	fput(file);



out_nattch:

	mutex_lock(&shm_ids(ns).mutex);

	shp = shm_lock(ns, shmid);

	down_write(&shm_ids(ns).rw_mutex);

	shp = shm_lock_down(ns, shmid);

	BUG_ON(IS_ERR(shp));

	shp->shm_nattch--;

	if(shp->shm_nattch == 0 &&
@@ -1007,7 +1032,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr) 
		shm_destroy(ns, shp);

	else

		shm_unlock(shp);

	mutex_unlock(&shm_ids(ns).mutex);

	up_write(&shm_ids(ns).rw_mutex);



out:

	return err;

ipc/util.c

+62 −16
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/proc_fs.h>

#include <linux/audit.h>

#include <linux/nsproxy.h>

#include <linux/rwsem.h>



#include <asm/unistd.h>
@@ -136,7 +137,7 @@ __initcall(ipc_init); 
 

void ipc_init_ids(struct ipc_ids *ids)

{

	mutex_init(&ids->mutex);

	init_rwsem(&ids->rw_mutex);



	ids->in_use = 0;

	ids->seq = 0;
@@ -191,7 +192,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header, 
 *	@ids: Identifier set

 *	@key: The key to find

 *	

 *	Requires ipc_ids.mutex locked.

 *	Requires ipc_ids.rw_mutex locked.

 *	Returns the LOCKED pointer to the ipc structure if found or NULL

 *	if not.

 *	If key is found ipc points to the owning ipc structure
@@ -225,7 +226,7 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key) 
 *	ipc_get_maxid 	-	get the last assigned id

 *	@ids: IPC identifier set

 *

 *	Called with ipc_ids.mutex held.

 *	Called with ipc_ids.rw_mutex held.

 */



int ipc_get_maxid(struct ipc_ids *ids)
@@ -263,7 +264,7 @@ int ipc_get_maxid(struct ipc_ids *ids) 
 *	is returned. The 'new' entry is returned in a locked state on success.

 *	On failure the entry is not locked and -1 is returned.

 *

 *	Called with ipc_ids.mutex held.

 *	Called with ipc_ids.rw_mutex held as a writer.

 */

 

int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
@@ -316,9 +317,9 @@ int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, 
	if (!err)

		return -ENOMEM;



	mutex_lock(&ids->mutex);

	down_write(&ids->rw_mutex);

	err = ops->getnew(ns, params);

	mutex_unlock(&ids->mutex);

	up_write(&ids->rw_mutex);



	return err;

}
@@ -335,7 +336,7 @@ int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, 
 *

 *	On success, the IPC id is returned.

 *

 *	It is called with ipc_ids.mutex and ipcp->lock held.

 *	It is called with ipc_ids.rw_mutex and ipcp->lock held.

 */

static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,

			struct ipc_params *params)
@@ -376,7 +377,11 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, 


	err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);



	mutex_lock(&ids->mutex);

	/*

	 * Take the lock as a writer since we are potentially going to add

	 * a new entry + read locks are not "upgradable"

	 */

	down_write(&ids->rw_mutex);

	ipcp = ipc_findkey(ids, params->key);

	if (ipcp == NULL) {

		/* key not used */
@@ -404,7 +409,7 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, 
		}

		ipc_unlock(ipcp);

	}

	mutex_unlock(&ids->mutex);

	up_write(&ids->rw_mutex);



	return err;

}
@@ -415,8 +420,8 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, 
 *	@ids: IPC identifier set

 *	@ipcp: ipc perm structure containing the identifier to remove

 *

 *	ipc_ids.mutex and the spinlock for this ID are held before this

 *	function is called, and remain locked on the exit.

 *	ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held

 *	before this function is called, and remain locked on the exit.

 */

 

void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
@@ -680,15 +685,17 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out) 
}



/**

 * ipc_lock - Lock an ipc structure

 * ipc_lock - Lock an ipc structure without rw_mutex held

 * @ids: IPC identifier set

 * @id: ipc id to look for

 *

 * Look for an id in the ipc ids idr and lock the associated ipc object.

 *

 * ipc_ids.mutex is not necessarily held before this function is called,

 * that's why we enter a RCU read section.

 * The ipc object is locked on exit.

 *

 * This is the routine that should be called when the rw_mutex is not already

 * held, i.e. idr tree not protected: it protects the idr tree in read mode

 * during the idr_find().

 */



struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
@@ -696,13 +703,18 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) 
	struct kern_ipc_perm *out;

	int lid = ipcid_to_idx(id);



	down_read(&ids->rw_mutex);



	rcu_read_lock();

	out = idr_find(&ids->ipcs_idr, lid);

	if (out == NULL) {

		rcu_read_unlock();

		up_read(&ids->rw_mutex);

		return ERR_PTR(-EINVAL);

	}



	up_read(&ids->rw_mutex);



	spin_lock(&out->lock);

	

	/* ipc_rmid() may have already freed the ID while ipc_lock
@@ -717,6 +729,40 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) 
	return out;

}



/**

 * ipc_lock_down - Lock an ipc structure with rw_sem held

 * @ids: IPC identifier set

 * @id: ipc id to look for

 *

 * Look for an id in the ipc ids idr and lock the associated ipc object.

 *

 * The ipc object is locked on exit.

 *

 * This is the routine that should be called when the rw_mutex is already

 * held, i.e. idr tree protected.

 */



struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *ids, int id)

{

	struct kern_ipc_perm *out;

	int lid = ipcid_to_idx(id);



	rcu_read_lock();

	out = idr_find(&ids->ipcs_idr, lid);

	if (out == NULL) {

		rcu_read_unlock();

		return ERR_PTR(-EINVAL);

	}



	spin_lock(&out->lock);



	/*

	 * No need to verify that the structure is still valid since the

	 * rw_mutex is held.

	 */

	return out;

}



#ifdef __ARCH_WANT_IPC_PARSE_VERSION
@@ -808,7 +854,7 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos) 
	 * Take the lock - this will be released by the corresponding

	 * call to stop().

	 */

	mutex_lock(&ids->mutex);

	down_read(&ids->rw_mutex);



	/* pos < 0 is invalid */

	if (*pos < 0)
@@ -835,7 +881,7 @@ static void sysvipc_proc_stop(struct seq_file *s, void *it) 


	ids = iter->ns->ids[iface->ids];

	/* Release the lock we took in start() */

	mutex_unlock(&ids->mutex);

	up_read(&ids->rw_mutex);

}



static int sysvipc_proc_show(struct seq_file *s, void *it)

ipc/util.h

+26 −2
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ struct ipc_ids { 
	int in_use;

	unsigned short seq;

	unsigned short seq_max;

	struct mutex mutex;

	struct rw_semaphore rw_mutex;

	struct idr ipcs_idr;

};
@@ -81,8 +81,10 @@ void __init ipc_init_proc_interface(const char *path, const char *header, 


#define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)



/* must be called with ids->mutex acquired.*/

/* must be called with ids->rw_mutex acquired for writing */

int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);



/* must be called with ids->rw_mutex acquired for reading */

int ipc_get_maxid(struct ipc_ids *);



/* must be called with both locks acquired. */
@@ -107,6 +109,11 @@ void* ipc_rcu_alloc(int size); 
void ipc_rcu_getref(void *ptr);

void ipc_rcu_putref(void *ptr);



/*

 * ipc_lock_down: called with rw_mutex held

 * ipc_lock: called without that lock held

 */

struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *, int);

struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);



void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
@@ -155,6 +162,23 @@ static inline void ipc_unlock(struct kern_ipc_perm *perm) 
	rcu_read_unlock();

}



static inline struct kern_ipc_perm *ipc_lock_check_down(struct ipc_ids *ids,

						int id)

{

	struct kern_ipc_perm *out;



	out = ipc_lock_down(ids, id);

	if (IS_ERR(out))

		return out;



	if (ipc_checkid(ids, out, id)) {

		ipc_unlock(out);

		return ERR_PTR(-EIDRM);

	}



	return out;

}



static inline struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids,

						int id)

{