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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

77
ipc/shm.c
View File

@ -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 @@ no_file:
}
/*
* 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 @@ invalid:
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 @@ out_nattch:
shm_destroy(ns, shp);
else
shm_unlock(shp);
mutex_unlock(&shm_ids(ns).mutex);
up_write(&shm_ids(ns).rw_mutex);
out:
return err;