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

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
......@@ -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);
......
......@@ -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;
......
......@@ -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;
......
......@@ -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)
......
......@@ -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);