Andrew Morton wrote:
On Tue, 18 Sep 2007 16:55:19 +0200 Nadia Derbey <[email protected]> wrote:
This patch fixes the missing rcu_read_(un)lock in the ipc code
Thanks. Could you please check the code comments in ipc/util.c for
accuracy and completeness sometime?
Done - see attachment.
Hope I didn't forget / add some wrong stuff ;-)
BTW this patch also fixes a missing lock in shm_get_stat().
Regards,
Nadia
This patch fixes the wrong / obsolete comments in the ipc code.
Also adds a missing lock around ipc_get_maxid() in shm_get_stat().
Signed-off-by: Nadia Derbey <[email protected]>
---
This patch applies on top of 2.6.23-rc6-mm1 + the previous IPC patches.
ipc/msg.c | 14 +++++++++-
ipc/sem.c | 14 ++++++++++
ipc/shm.c | 39 ++++++++++++++++++++----------
ipc/util.c | 78 +++++++++++++++++++++++++++++++++++++++----------------------
ipc/util.h | 18 ++++++++++++--
5 files changed, 118 insertions(+), 45 deletions(-)
Index: linux-2.6.23-rc6-mm1/ipc/util.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/util.c 2007-09-21 08:00:41.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/util.c 2007-09-21 10:32:03.000000000 +0200
@@ -194,7 +194,7 @@ void __init ipc_init_proc_interface(cons
* Requires ipc_ids.mutex locked.
* Returns the LOCKED pointer to the ipc structure if found or NULL
* if not.
- * If key is found ipc contains its ipc structure
+ * If key is found ipc points to the owning ipc structure
*/
static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
@@ -258,10 +258,10 @@ int ipc_get_maxid(struct ipc_ids *ids)
* @new: new IPC permission set
* @size: limit for the number of used ids
*
- * Add an entry 'new' to the IPC idr. The permissions object is
+ * Add an entry 'new' to the IPC ids idr. The permissions object is
* initialised and the first free entry is set up and the id assigned
- * is returned. The list is returned in a locked state on success.
- * On failure the list is not locked and -1 is returned.
+ * 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.
*/
@@ -270,10 +270,6 @@ int ipc_addid(struct ipc_ids* ids, struc
{
int id, err;
- /*
- * rcu_dereference()() is not needed here since
- * ipc_ids.mutex is held
- */
if (size > IPCMNI)
size = IPCMNI;
@@ -303,12 +299,12 @@ int ipc_addid(struct ipc_ids* ids, struc
/**
* ipcget_new - create a new ipc object
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is IPC_PRIVATE.
*/
int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
@@ -330,9 +326,16 @@ int ipcget_new(struct ipc_namespace *ns,
/**
* ipc_check_perms - check security and permissions for an IPC
* @ipcp: ipc permission set
- * @ids: identifer set
* @ops: the actual security routine to call
* @params: its parameters
+ *
+ * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE and that key already exists in the
+ * ids IDR.
+ *
+ * On success, the IPC id is returned.
+ *
+ * It is called with ipc_ids.mutex and ipcp->lock held.
*/
static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,
struct ipc_params *params)
@@ -353,12 +356,16 @@ static int ipc_check_perms(struct kern_i
/**
* ipcget_public - get an ipc object or create a new one
* @ns: namespace
- * @ids: identifer set
+ * @ids: IPC identifer set
* @ops: the actual creation routine to call
* @params: its parameters
*
- * This routine is called sys_msgget, sys_semget() and sys_shmget() when
- * the key is not IPC_PRIVATE
+ * This routine is called by sys_msgget, sys_semget() and sys_shmget()
+ * when the key is not IPC_PRIVATE.
+ * It adds a new entry if the key is not found and does some permission
+ * / security checkings if the key is found.
+ *
+ * On success, the ipc id is returned.
*/
int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
@@ -389,6 +396,10 @@ int ipcget_public(struct ipc_namespace *
if (ops->more_checks)
err = ops->more_checks(ipcp, params);
if (!err)
+ /*
+ * ipc_check_perms returns the IPC id on
+ * success
+ */
err = ipc_check_perms(ipcp, ops, params);
}
ipc_unlock(ipcp);
@@ -401,12 +412,9 @@ int ipcget_public(struct ipc_namespace *
/**
* ipc_rmid - remove an IPC identifier
- * @ids: identifier set
- * @id: ipc perm structure containing the identifier to remove
+ * @ids: IPC identifier set
+ * @ipcp: ipc perm structure containing the identifier to remove
*
- * The identifier must be valid, and in use. The kernel will panic if
- * fed an invalid identifier. The entry is removed and internal
- * variables recomputed.
* ipc_ids.mutex and the spinlock for this ID are held before this
* function is called, and remain locked on the exit.
*/
@@ -558,10 +566,12 @@ static void ipc_do_vfree(struct work_str
*/
static void ipc_schedule_free(struct rcu_head *head)
{
- struct ipc_rcu_grace *grace =
- container_of(head, struct ipc_rcu_grace, rcu);
- struct ipc_rcu_sched *sched =
- container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
+ struct ipc_rcu_grace *grace;
+ struct ipc_rcu_sched *sched;
+
+ grace = container_of(head, struct ipc_rcu_grace, rcu);
+ sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
+ data[0]);
INIT_WORK(&sched->work, ipc_do_vfree);
schedule_work(&sched->work);
@@ -650,7 +660,7 @@ void kernel_to_ipc64_perm (struct kern_i
}
/**
- * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
+ * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
* @in: new style IPC permissions
* @out: old style IPC permissions
*
@@ -669,6 +679,18 @@ void ipc64_perm_to_ipc_perm (struct ipc6
out->seq = in->seq;
}
+/**
+ * ipc_lock - Lock an ipc structure
+ * @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.
+ */
+
struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
{
struct kern_ipc_perm *out;
@@ -771,8 +793,8 @@ static void *sysvipc_proc_next(struct se
}
/*
- * File positions: pos 0 -> header, pos n -> ipc id + 1.
- * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
+ * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
+ * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
{
@@ -807,7 +829,7 @@ static void sysvipc_proc_stop(struct seq
struct ipc_proc_iface *iface = iter->iface;
struct ipc_ids *ids;
- /* If we had a locked segment, release it */
+ /* If we had a locked structure, release it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
Index: linux-2.6.23-rc6-mm1/ipc/util.h
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/util.h 2007-09-21 08:00:41.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/util.h 2007-09-21 10:30:27.000000000 +0200
@@ -54,7 +54,7 @@ struct ipc_params {
* the calls to sys_msgget(), sys_semget(), sys_shmget()
* . routine to call to create a new ipc object. Can be one of newque,
* newary, newseg
- * . routine to call to call to check permissions for a new ipc object.
+ * . routine to call to check permissions for a new ipc object.
* Can be one of security_msg_associate, security_sem_associate,
* security_shm_associate
* . routine to call for an extra check if needed
@@ -88,7 +88,8 @@ int ipc_get_maxid(struct ipc_ids *);
/* must be called with both locks acquired. */
void ipc_rmid(struct ipc_ids *, struct kern_ipc_perm *);
-int ipcperms (struct kern_ipc_perm *ipcp, short flg);
+/* must be called with ipcp locked */
+int ipcperms(struct kern_ipc_perm *ipcp, short flg);
/* for rare, potentially huge allocations.
* both function can sleep
@@ -131,6 +132,9 @@ static inline int ipc_buildid(struct ipc
return SEQ_MULTIPLIER * seq + id;
}
+/*
+ * Must be called with ipcp locked
+ */
static inline int ipc_checkid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp,
int uid)
{
@@ -168,6 +172,16 @@ static inline struct kern_ipc_perm *ipc_
return out;
}
+/**
+ * ipcget - Common sys_*get() code
+ * @ns : namsepace
+ * @ids : IPC identifier set
+ * @ops : operations to be called on ipc object creation, permission checks
+ * and further checks
+ * @params : the parameters needed by the previous operations.
+ *
+ * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
+ */
static inline int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params)
{
Index: linux-2.6.23-rc6-mm1/ipc/msg.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/msg.c 2007-09-21 08:00:41.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/msg.c 2007-09-21 10:33:08.000000000 +0200
@@ -156,6 +156,13 @@ static inline void msg_rmid(struct ipc_n
ipc_rmid(&msg_ids(ns), &s->q_perm);
}
+/**
+ * newque - Create a new msg queue
+ * @ns: namespace
+ * @params: ptr to the structure that contains the key and msgflg
+ *
+ * Called with msg_ids.mutex held
+ */
static int newque(struct ipc_namespace *ns, struct ipc_params *params)
{
struct msg_queue *msq;
@@ -250,8 +257,8 @@ static void expunge_all(struct msg_queue
/*
* freeque() wakes up waiters on the sender and receiver waiting queue,
- * removes the message queue from message queue ID
- * IDR, and cleans up all the messages associated with this queue.
+ * 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.
@@ -278,6 +285,9 @@ static void freeque(struct ipc_namespace
ipc_rcu_putref(msq);
}
+/*
+ * Called with msg_ids.mutex and ipcp locked.
+ */
static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
{
struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
Index: linux-2.6.23-rc6-mm1/ipc/sem.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/sem.c 2007-09-21 08:00:41.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/sem.c 2007-09-21 10:33:50.000000000 +0200
@@ -228,6 +228,14 @@ static inline void sem_rmid(struct ipc_n
*/
#define IN_WAKEUP 1
+/**
+ * newary - Create a new semaphore set
+ * @ns: namespace
+ * @params: ptr to the structure that contains key, semflg and nsems
+ *
+ * Called with sem_ids.mutex held
+ */
+
static int newary(struct ipc_namespace *ns, struct ipc_params *params)
{
int id;
@@ -281,6 +289,9 @@ static int newary(struct ipc_namespace *
}
+/*
+ * Called with sem_ids.mutex and ipcp locked.
+ */
static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
{
struct sem_array *sma;
@@ -289,6 +300,9 @@ static inline int sem_security(struct ke
return security_sem_associate(sma, semflg);
}
+/*
+ * Called with sem_ids.mutex and ipcp locked.
+ */
static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
struct ipc_params *params)
{
Index: linux-2.6.23-rc6-mm1/ipc/shm.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/shm.c 2007-09-21 08:00:41.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/shm.c 2007-09-21 10:34:25.000000000 +0200
@@ -82,6 +82,10 @@ static void __shm_init_ns(struct ipc_nam
ipc_init_ids(ids);
}
+/*
+ * Called with shm_ids.mutex and the shp structure locked.
+ * Only shm_ids.mutex remains locked on exit.
+ */
static void do_shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *shp)
{
if (shp->shm_nattch){
@@ -182,6 +186,7 @@ static void shm_open(struct vm_area_stru
/*
* shm_destroy - free the struct shmid_kernel
*
+ * @ns: namespace
* @shp: struct to free
*
* It has to be called with shp and shm_ids.mutex locked,
@@ -343,6 +348,14 @@ static struct vm_operations_struct shm_v
#endif
};
+/**
+ * newseg - Create a new shared memory segment
+ * @ns: namespace
+ * @params: ptr to the structure that contains key, size and shmflg
+ *
+ * Called with shm_ids.mutex held
+ */
+
static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
{
key_t key = params->key;
@@ -428,6 +441,9 @@ no_file:
return error;
}
+/*
+ * Called with shm_ids.mutex and ipcp locked.
+ */
static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg)
{
struct shmid_kernel *shp;
@@ -436,6 +452,9 @@ static inline int shm_security(struct ke
return security_shm_associate(shp, shmflg);
}
+/*
+ * Called with shm_ids.mutex and ipcp locked.
+ */
static inline int shm_more_checks(struct kern_ipc_perm *ipcp,
struct ipc_params *params)
{
@@ -558,6 +577,9 @@ static inline unsigned long copy_shminfo
}
}
+/*
+ * Called with shm_ids.mutex held
+ */
static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
unsigned long *swp)
{
@@ -573,18 +595,6 @@ static void shm_get_stat(struct ipc_name
struct shmid_kernel *shp;
struct inode *inode;
- /*
- * idr_find() is called via shm_get(), so with shm_ids.mutex
- * locked. Since ipc_addid() is also called with
- * shm_ids.mutex down, there is no need to add read barriers
- * here to gurantee the writes in ipc_addid() are seen in
- * order here (for Alpha).
- * However idr_find() itself does not necessary require
- * ipc_ids.mutex down. So if idr_find() is used by other
- * places without ipc_ids.mutex down, then it needs read
- * read memory barriers as ipc_lock() does.
- */
-
shp = idr_find(&shm_ids(ns).ipcs_idr, next_id);
if (shp == NULL)
continue;
@@ -638,8 +648,11 @@ asmlinkage long sys_shmctl (int shmid, i
shminfo.shmmin = SHMMIN;
if(copy_shminfo_to_user (buf, &shminfo, version))
return -EFAULT;
- /* reading a integer is always atomic */
+
+ mutex_lock(&shm_ids(ns).mutex);
err = ipc_get_maxid(&shm_ids(ns));
+ mutex_unlock(&shm_ids(ns).mutex);
+
if(err<0)
err = 0;
goto out;
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