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ipc,shm: make shmctl_nolock lockless

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While the INFO cmd doesn't take the ipc lock, the STAT commands do acquire
it unnecessarily.  We can do the permissions and security checks only
holding the rcu lock.

[akpm@linux-foundation.org: coding-style fixes]
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: 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 14:26:20 -07:00 committed by Linus Torvalds
parent 68eccc1dc3
commit c97cb9ccab
1 changed files with 12 additions and 7 deletions
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19
ipc/shm.c
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@ -882,27 +882,31 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
struct shmid64_ds tbuf;
int result;
rcu_read_lock();
if (cmd == SHM_STAT) {
shp = shm_lock(ns, shmid);
shp = shm_obtain_object(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
goto out;
goto out_unlock;
}
result = shp->shm_perm.id;
} else {
shp = shm_lock_check(ns, shmid);
shp = shm_obtain_object_check(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
goto out;
goto out_unlock;
}
result = 0;
}
err = -EACCES;
if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
goto out_unlock;
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;
memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
tbuf.shm_segsz = shp->shm_segsz;
@ -912,8 +916,9 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
tbuf.shm_cpid = shp->shm_cprid;
tbuf.shm_lpid = shp->shm_lprid;
tbuf.shm_nattch = shp->shm_nattch;
shm_unlock(shp);
if(copy_shmid_to_user (buf, &tbuf, version))
rcu_read_unlock();
if (copy_shmid_to_user(buf, &tbuf, version))
err = -EFAULT;
else
err = result;
@ -924,7 +929,7 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
}
out_unlock:
shm_unlock(shp);
rcu_read_unlock();
out:
return err;
}