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Commit c97cb9cc authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
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ipc,shm: make shmctl_nolock lockless


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: 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 avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 68eccc1d
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...@@ -882,27 +882,31 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, ...@@ -882,27 +882,31 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
struct shmid64_ds tbuf; struct shmid64_ds tbuf;
int result; int result;
rcu_read_lock();
if (cmd == SHM_STAT) { if (cmd == SHM_STAT) {
shp = shm_lock(ns, shmid); shp = shm_obtain_object(ns, shmid);
if (IS_ERR(shp)) { if (IS_ERR(shp)) {
err = PTR_ERR(shp); err = PTR_ERR(shp);
goto out; goto out_unlock;
} }
result = shp->shm_perm.id; result = shp->shm_perm.id;
} else { } else {
shp = shm_lock_check(ns, shmid); 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;
} }
result = 0; result = 0;
} }
err = -EACCES; err = -EACCES;
if (ipcperms(ns, &shp->shm_perm, S_IRUGO)) if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
goto out_unlock; goto out_unlock;
err = security_shm_shmctl(shp, cmd); err = security_shm_shmctl(shp, cmd);
if (err) if (err)
goto out_unlock; goto out_unlock;
memset(&tbuf, 0, sizeof(tbuf)); memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm); kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
tbuf.shm_segsz = shp->shm_segsz; tbuf.shm_segsz = shp->shm_segsz;
...@@ -912,7 +916,8 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, ...@@ -912,7 +916,8 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
tbuf.shm_cpid = shp->shm_cprid; tbuf.shm_cpid = shp->shm_cprid;
tbuf.shm_lpid = shp->shm_lprid; tbuf.shm_lpid = shp->shm_lprid;
tbuf.shm_nattch = shp->shm_nattch; tbuf.shm_nattch = shp->shm_nattch;
shm_unlock(shp); rcu_read_unlock();
if (copy_shmid_to_user(buf, &tbuf, version)) if (copy_shmid_to_user(buf, &tbuf, version))
err = -EFAULT; err = -EFAULT;
else else
...@@ -924,7 +929,7 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid, ...@@ -924,7 +929,7 @@ static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
} }
out_unlock: out_unlock:
shm_unlock(shp); rcu_read_unlock();
out: out:
return err; return err;
} }
......
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