2006-08-23 19:48:34

by Eric Paris

Subject: [PATCH] SELinux: 3/3 convert sbsec semaphore to a mutex

This patch converts the semaphore in the superblock security struct to a
mutex. No locking changes or other code changes are done.

This is being targeted for 2.6.19

Signed-off-by: Eric Paris <[email protected]>
Acked-by: Stephen Smalley <[email protected]>

security/selinux/hooks.c | 7 +++----
security/selinux/include/objsec.h | 2 +-
2 files changed, 4 insertions(+), 5 deletions(-)

--- linux-2.6-sem-changes/security/selinux/include/objsec.h.patch3 2006-08-03 14:04:07.000000000 -0400
+++ linux-2.6-sem-changes/security/selinux/include/objsec.h 2006-08-03 14:18:44.000000000 -0400
@@ -63,7 +63,7 @@ struct superblock_security_struct {
unsigned int behavior; /* labeling behavior */
unsigned char initialized; /* initialization flag */
unsigned char proc; /* proc fs */
- struct semaphore sem;
+ struct mutex lock;
struct list_head isec_head;
spinlock_t isec_lock;
};
--- linux-2.6-sem-changes/security/selinux/hooks.c.patch3 2006-08-02 14:29:28.000000000 -0400
+++ linux-2.6-sem-changes/security/selinux/hooks.c 2006-08-03 14:21:48.000000000 -0400
@@ -49,7 +49,6 @@
#include <net/ip.h> /* for sysctl_local_port_range[] */
#include <net/tcp.h> /* struct or_callable used in sock_rcv_skb */
#include <asm/uaccess.h>
-#include <asm/semaphore.h>
#include <asm/ioctls.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
@@ -240,7 +239,7 @@ static int superblock_alloc_security(str
if (!sbsec)
return -ENOMEM;

- init_MUTEX(&sbsec->sem);
+ mutex_init(&sbsec->lock);
INIT_LIST_HEAD(&sbsec->list);
INIT_LIST_HEAD(&sbsec->isec_head);
spin_lock_init(&sbsec->isec_lock);
@@ -595,7 +594,7 @@ static int superblock_doinit(struct supe
struct inode *inode = root->d_inode;
int rc = 0;

- down(&sbsec->sem);
+ mutex_lock(&sbsec->lock);
if (sbsec->initialized)
goto out;

@@ -690,7 +689,7 @@ next_inode:
}
spin_unlock(&sbsec->isec_lock);
out:
- up(&sbsec->sem);
+ mutex_unlock(&sbsec->lock);
return rc;
}

2006-08-23 20:05:33

by James Morris

Subject: Re: [PATCH] SELinux: 3/3 convert sbsec semaphore to a mutex

On Wed, 23 Aug 2006, Eric Paris wrote:

> This patch converts the semaphore in the superblock security struct to a
> mutex. No locking changes or other code changes are done.
>
> This is being targeted for 2.6.19
>
> Signed-off-by: Eric Paris <[email protected]>
> Acked-by: Stephen Smalley <[email protected]>

Acked-by: James Morris <[email protected]>


--
James Morris
<[email protected]>

2006-08-23 21:04:57

by Andrew Morton

Subject: Re: [PATCH] SELinux: 3/3 convert sbsec semaphore to a mutex

On Wed, 23 Aug 2006 15:50:37 -0400
Eric Paris <[email protected]> wrote:

> This patch converts the semaphore in the superblock security struct to a
> mutex. No locking changes or other code changes are done.
>
> This is being targeted for 2.6.19
>
> Signed-off-by: Eric Paris <[email protected]>
> Acked-by: Stephen Smalley <[email protected]>
>
> security/selinux/hooks.c | 7 +++----
> security/selinux/include/objsec.h | 2 +-
> 2 files changed, 4 insertions(+), 5 deletions(-)
>
> --- linux-2.6-sem-changes/security/selinux/include/objsec.h.patch3 2006-08-03 14:04:07.000000000 -0400
> +++ linux-2.6-sem-changes/security/selinux/include/objsec.h 2006-08-03 14:18:44.000000000 -0400
> @@ -63,7 +63,7 @@ struct superblock_security_struct {
> unsigned int behavior; /* labeling behavior */
> unsigned char initialized; /* initialization flag */
> unsigned char proc; /* proc fs */
> - struct semaphore sem;
> + struct mutex lock;
> struct list_head isec_head;
> spinlock_t isec_lock;
> };
> --- linux-2.6-sem-changes/security/selinux/hooks.c.patch3 2006-08-02 14:29:28.000000000 -0400
> +++ linux-2.6-sem-changes/security/selinux/hooks.c 2006-08-03 14:21:48.000000000 -0400
> @@ -49,7 +49,6 @@
> #include <net/ip.h> /* for sysctl_local_port_range[] */
> #include <net/tcp.h> /* struct or_callable used in sock_rcv_skb */
> #include <asm/uaccess.h>
> -#include <asm/semaphore.h>
> #include <asm/ioctls.h>
> #include <linux/bitops.h>
> #include <linux/interrupt.h>
> @@ -240,7 +239,7 @@ static int superblock_alloc_security(str
> if (!sbsec)
> return -ENOMEM;
>
> - init_MUTEX(&sbsec->sem);
> + mutex_init(&sbsec->lock);
> INIT_LIST_HEAD(&sbsec->list);
> INIT_LIST_HEAD(&sbsec->isec_head);
> spin_lock_init(&sbsec->isec_lock);
> @@ -595,7 +594,7 @@ static int superblock_doinit(struct supe
> struct inode *inode = root->d_inode;
> int rc = 0;
>
> - down(&sbsec->sem);
> + mutex_lock(&sbsec->lock);
> if (sbsec->initialized)
> goto out;
>
> @@ -690,7 +689,7 @@ next_inode:
> }
> spin_unlock(&sbsec->isec_lock);
> out:
> - up(&sbsec->sem);
> + mutex_unlock(&sbsec->lock);
> return rc;
> }
>
>

Does this lock actually do anything?

2006-08-24 12:30:46

by Stephen Smalley

Subject: Re: [PATCH] SELinux: 3/3 convert sbsec semaphore to a mutex

On Wed, 2006-08-23 at 14:04 -0700, Andrew Morton wrote:
> On Wed, 23 Aug 2006 15:50:37 -0400
> Eric Paris <[email protected]> wrote:
>
> > This patch converts the semaphore in the superblock security struct to a
> > mutex. No locking changes or other code changes are done.
> >
> > This is being targeted for 2.6.19
> >
> > Signed-off-by: Eric Paris <[email protected]>
> > Acked-by: Stephen Smalley <[email protected]>
> >
> > security/selinux/hooks.c | 7 +++----
> > security/selinux/include/objsec.h | 2 +-
> > 2 files changed, 4 insertions(+), 5 deletions(-)
> >
> > --- linux-2.6-sem-changes/security/selinux/include/objsec.h.patch3 2006-08-03 14:04:07.000000000 -0400
> > +++ linux-2.6-sem-changes/security/selinux/include/objsec.h 2006-08-03 14:18:44.000000000 -0400
> > @@ -63,7 +63,7 @@ struct superblock_security_struct {
> > unsigned int behavior; /* labeling behavior */
> > unsigned char initialized; /* initialization flag */
> > unsigned char proc; /* proc fs */
> > - struct semaphore sem;
> > + struct mutex lock;
> > struct list_head isec_head;
> > spinlock_t isec_lock;
> > };
> > --- linux-2.6-sem-changes/security/selinux/hooks.c.patch3 2006-08-02 14:29:28.000000000 -0400
> > +++ linux-2.6-sem-changes/security/selinux/hooks.c 2006-08-03 14:21:48.000000000 -0400
> > @@ -49,7 +49,6 @@
> > #include <net/ip.h> /* for sysctl_local_port_range[] */
> > #include <net/tcp.h> /* struct or_callable used in sock_rcv_skb */
> > #include <asm/uaccess.h>
> > -#include <asm/semaphore.h>
> > #include <asm/ioctls.h>
> > #include <linux/bitops.h>
> > #include <linux/interrupt.h>
> > @@ -240,7 +239,7 @@ static int superblock_alloc_security(str
> > if (!sbsec)
> > return -ENOMEM;
> >
> > - init_MUTEX(&sbsec->sem);
> > + mutex_init(&sbsec->lock);
> > INIT_LIST_HEAD(&sbsec->list);
> > INIT_LIST_HEAD(&sbsec->isec_head);
> > spin_lock_init(&sbsec->isec_lock);
> > @@ -595,7 +594,7 @@ static int superblock_doinit(struct supe
> > struct inode *inode = root->d_inode;
> > int rc = 0;
> >
> > - down(&sbsec->sem);
> > + mutex_lock(&sbsec->lock);
> > if (sbsec->initialized)
> > goto out;
> >
> > @@ -690,7 +689,7 @@ next_inode:
> > }
> > spin_unlock(&sbsec->isec_lock);
> > out:
> > - up(&sbsec->sem);
> > + mutex_unlock(&sbsec->lock);
> > return rc;
> > }
> >
> >
>
> Does this lock actually do anything?

The function is called from vfs_kern_mount normally, and from
selinux_complete_init just for the initial setup after initial policy
load. The lock is for the initialization of the superblock security
struct. Strictly speaking, we can't race from vfs_kern_mount since the
caller holds s_umount write lock already, but I didn't think we should
rely on that here. Eric noticed that as well when he was preparing the
sem->mutex conversion patch and was originally going to drop the lock
altogether.

--
Stephen Smalley
National Security Agency