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Commit c2c737a0 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
Browse files

ipc,shm: shorten critical region for shmat 



Similar to other system calls, acquire the kern_ipc_perm lock after doing
the initial permission and security checks.

[sasha.levin@oracle.com: dont leave do_shmat with rcu lock held]
Signed-off-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f42569b1

ipc/shm.c

+10 −4
Original line number Diff line number Diff line
@@ -19,6 +19,9 @@ 
 * namespaces support

 * OpenVZ, SWsoft Inc.

 * Pavel Emelianov <xemul@openvz.org>

 *

 * Better ipc lock (kern_ipc_perm.lock) handling

 * Davidlohr Bueso <davidlohr.bueso@hp.com>, June 2013.

 */



#include <linux/slab.h>
@@ -1086,10 +1089,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, 
	 * additional creator id...

	 */

	ns = current->nsproxy->ipc_ns;

	shp = shm_lock_check(ns, shmid);

	rcu_read_lock();

	shp = shm_obtain_object_check(ns, shmid);

	if (IS_ERR(shp)) {

		err = PTR_ERR(shp);

		goto out;

		goto out_unlock;

	}



	err = -EACCES;
@@ -1100,11 +1104,13 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, 
	if (err)

		goto out_unlock;



	ipc_lock_object(&shp->shm_perm);

	path = shp->shm_file->f_path;

	path_get(&path);

	shp->shm_nattch++;

	size = i_size_read(path.dentry->d_inode);

	shm_unlock(shp);

	ipc_unlock_object(&shp->shm_perm);

	rcu_read_unlock();



	err = -ENOMEM;

	sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
@@ -1175,7 +1181,7 @@ out_nattch: 
	return err;



out_unlock:

	shm_unlock(shp);

	rcu_read_unlock();

out:

	return err;

}