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ipc,shm: shorten critical region for shmctl 

With the *_INFO, *_STAT, IPC_RMID and IPC_SET commands already optimized,
deal with the remaining SHM_LOCK and SHM_UNLOCK commands.  Take the
shm_perm lock after doing the initial auditing and security checks.  The
rest of the logic remains unchanged.

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 14:26:21 -07:00 committed by Linus Torvalds
parent c97cb9ccab
commit 2caacaa82a
1 changed files with 25 additions and 24 deletions
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49
ipc/shm.c
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@ -940,10 +940,8 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
int err, version; int err, version;
struct ipc_namespace *ns; struct ipc_namespace *ns;
if (cmd < 0 || shmid < 0) { if (cmd < 0 || shmid < 0)
err = -EINVAL; return -EINVAL;
goto out;
}
version = ipc_parse_version(&cmd); version = ipc_parse_version(&cmd);
ns = current->nsproxy->ipc_ns; ns = current->nsproxy->ipc_ns;
@ -954,36 +952,40 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
case SHM_STAT: case SHM_STAT:
case IPC_STAT: case IPC_STAT:
return shmctl_nolock(ns, shmid, cmd, version, buf); return shmctl_nolock(ns, shmid, cmd, version, buf);
case IPC_RMID:
case IPC_SET:
return shmctl_down(ns, shmid, cmd, buf, version);
case SHM_LOCK: case SHM_LOCK:
case SHM_UNLOCK: case SHM_UNLOCK:
{ {
struct file *shm_file; struct file *shm_file;
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_unlock1;
} }
audit_ipc_obj(&(shp->shm_perm)); audit_ipc_obj(&(shp->shm_perm));
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock1;
ipc_lock_object(&shp->shm_perm);
if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) { if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
kuid_t euid = current_euid(); kuid_t euid = current_euid();
err = -EPERM; err = -EPERM;
if (!uid_eq(euid, shp->shm_perm.uid) && if (!uid_eq(euid, shp->shm_perm.uid) &&
!uid_eq(euid, shp->shm_perm.cuid)) !uid_eq(euid, shp->shm_perm.cuid))
goto out_unlock; goto out_unlock0;
if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK))
goto out_unlock; goto out_unlock0;
} }
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;
shm_file = shp->shm_file; shm_file = shp->shm_file;
if (is_file_hugepages(shm_file)) if (is_file_hugepages(shm_file))
goto out_unlock; goto out_unlock0;
if (cmd == SHM_LOCK) { if (cmd == SHM_LOCK) {
struct user_struct *user = current_user(); struct user_struct *user = current_user();
@ -992,32 +994,31 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
shp->shm_perm.mode |= SHM_LOCKED; shp->shm_perm.mode |= SHM_LOCKED;
shp->mlock_user = user; shp->mlock_user = user;
} }
goto out_unlock; goto out_unlock0;
} }
/* SHM_UNLOCK */ /* SHM_UNLOCK */
if (!(shp->shm_perm.mode & SHM_LOCKED)) if (!(shp->shm_perm.mode & SHM_LOCKED))
goto out_unlock; goto out_unlock0;
shmem_lock(shm_file, 0, shp->mlock_user); shmem_lock(shm_file, 0, shp->mlock_user);
shp->shm_perm.mode &= ~SHM_LOCKED; shp->shm_perm.mode &= ~SHM_LOCKED;
shp->mlock_user = NULL; shp->mlock_user = NULL;
get_file(shm_file); get_file(shm_file);
shm_unlock(shp); ipc_unlock_object(&shp->shm_perm);
rcu_read_unlock();
shmem_unlock_mapping(shm_file->f_mapping); shmem_unlock_mapping(shm_file->f_mapping);
fput(shm_file); fput(shm_file);
goto out;
}
case IPC_RMID:
case IPC_SET:
err = shmctl_down(ns, shmid, cmd, buf, version);
return err; return err;
}
default: default:
return -EINVAL; return -EINVAL;
} }
out_unlock: out_unlock0:
shm_unlock(shp); ipc_unlock_object(&shp->shm_perm);
out: out_unlock1:
rcu_read_unlock();
return err; return err;
} }