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ipc,shm: shorten critical region for shmat

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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: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2013-09-11 14:26:23 -07:00 committed by Linus Torvalds
parent f42569b138
commit c2c737a046
1 changed files with 10 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

14
ipc/shm.c
View file

@ -19,6 +19,9 @@
* namespaces support * namespaces support
* OpenVZ, SWsoft Inc. * OpenVZ, SWsoft Inc.
* Pavel Emelianov <xemul@openvz.org> * 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> #include <linux/slab.h>
@ -1086,10 +1089,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
* additional creator id... * additional creator id...
*/ */
ns = current->nsproxy->ipc_ns; 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)) { if (IS_ERR(shp)) {
err = PTR_ERR(shp); err = PTR_ERR(shp);
goto out; goto out_unlock;
} }
err = -EACCES; err = -EACCES;
@ -1100,11 +1104,13 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
if (err) if (err)
goto out_unlock; goto out_unlock;
ipc_lock_object(&shp->shm_perm);
path = shp->shm_file->f_path; path = shp->shm_file->f_path;
path_get(&path); path_get(&path);
shp->shm_nattch++; shp->shm_nattch++;
size = i_size_read(path.dentry->d_inode); size = i_size_read(path.dentry->d_inode);
shm_unlock(shp); ipc_unlock_object(&shp->shm_perm);
rcu_read_unlock();
err = -ENOMEM; err = -ENOMEM;
sfd = kzalloc(sizeof(*sfd), GFP_KERNEL); sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
@ -1175,7 +1181,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
return err; return err;
out_unlock: out_unlock:
shm_unlock(shp); rcu_read_unlock();
out: out:
return err; return err;
} }