[PATCH] SELinux: change isec semaphore to a mutex

This patch converts the remaining isec->sem into a mutex.  Very similar
locking is provided as before only in the faster smaller mutex rather than a
semaphore.  An out_unlock path is introduced rather than the conditional
unlocking found in the original code.
Signed-off-by: NEric Paris <eparis@redhat.com>
Acked-by: NStephen Smalley <sds@tycho.nsa.gov>
Acked-by: NJames Morris <jmorris@namei.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

security/selinux/hooks.c

@@ -71,6 +71,7 @@
 #include <linux/audit.h>
 #include <linux/string.h>
 #include <linux/selinux.h>
+#include <linux/mutex.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -185,7 +186,7 @@ static int inode_alloc_security(struct inode *inode)
 		return -ENOMEM;
 
 	memset(isec, 0, sizeof(*isec));
-	init_MUTEX(&isec->sem);
+	mutex_init(&isec->lock);
 	INIT_LIST_HEAD(&isec->list);
 	isec->inode = inode;
 	isec->sid = SECINITSID_UNLABELED;
@@ -843,15 +844,13 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 	char *context = NULL;
 	unsigned len = 0;
 	int rc = 0;
-	int hold_sem = 0;
 
 	if (isec->initialized)
 		goto out;
 
-	down(&isec->sem);
-	hold_sem = 1;
+	mutex_lock(&isec->lock);
 	if (isec->initialized)
-		goto out;
+		goto out_unlock;
 
 	sbsec = inode->i_sb->s_security;
 	if (!sbsec->initialized) {
@@ -862,7 +861,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 		if (list_empty(&isec->list))
 			list_add(&isec->list, &sbsec->isec_head);
 		spin_unlock(&sbsec->isec_lock);
-		goto out;
+		goto out_unlock;
 	}
 
 	switch (sbsec->behavior) {
@@ -885,7 +884,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 			printk(KERN_WARNING "%s:  no dentry for dev=%s "
 			       "ino=%ld\n", __FUNCTION__, inode->i_sb->s_id,
 			       inode->i_ino);
-			goto out;
+			goto out_unlock;
 		}
 
 		len = INITCONTEXTLEN;
@@ -893,7 +892,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 		if (!context) {
 			rc = -ENOMEM;
 			dput(dentry);
-			goto out;
+			goto out_unlock;
 		}
 		rc = inode->i_op->getxattr(dentry, XATTR_NAME_SELINUX,
 					   context, len);
@@ -903,7 +902,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 						   NULL, 0);
 			if (rc < 0) {
 				dput(dentry);
-				goto out;
+				goto out_unlock;
 			}
 			kfree(context);
 			len = rc;
@@ -911,7 +910,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 			if (!context) {
 				rc = -ENOMEM;
 				dput(dentry);
-				goto out;
+				goto out_unlock;
 			}
 			rc = inode->i_op->getxattr(dentry,
 						   XATTR_NAME_SELINUX,
@@ -924,7 +923,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 				       "%d for dev=%s ino=%ld\n", __FUNCTION__,
 				       -rc, inode->i_sb->s_id, inode->i_ino);
 				kfree(context);
-				goto out;
+				goto out_unlock;
 			}
 			/* Map ENODATA to the default file SID */
 			sid = sbsec->def_sid;
@@ -960,7 +959,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 					     isec->sclass,
 					     &sid);
 		if (rc)
-			goto out;
+			goto out_unlock;
 		isec->sid = sid;
 		break;
 	case SECURITY_FS_USE_MNTPOINT:
@@ -978,7 +977,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 							  isec->sclass,
 							  &sid);
 				if (rc)
-					goto out;
+					goto out_unlock;
 				isec->sid = sid;
 			}
 		}
@@ -987,12 +986,11 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 
 	isec->initialized = 1;
 
+out_unlock:
+	mutex_unlock(&isec->lock);
 out:
 	if (isec->sclass == SECCLASS_FILE)
 		isec->sclass = inode_mode_to_security_class(inode->i_mode);
-
-	if (hold_sem)
-		up(&isec->sem);
 	return rc;
 }
 

security/selinux/include/objsec.h

@@ -44,7 +44,7 @@ struct inode_security_struct {
 	u32 sid;             /* SID of this object */
 	u16 sclass;       /* security class of this object */
 	unsigned char initialized;     /* initialization flag */
-	struct semaphore sem;
+	struct mutex lock;
 	unsigned char inherit;         /* inherit SID from parent entry */
 };
 

security/selinux/ss/services.c

@@ -2578,7 +2578,7 @@ int selinux_netlbl_inode_permission(struct inode *inode, int mask)
 	sock = SOCKET_I(inode);
 	isec = inode->i_security;
 	sksec = sock->sk->sk_security;
-	down(&isec->sem);
+	mutex_lock(&isec->lock);
 	if (unlikely(sksec->nlbl_state == NLBL_REQUIRE &&
 		     (mask & (MAY_WRITE | MAY_APPEND)))) {
 		lock_sock(sock->sk);
@@ -2586,7 +2586,7 @@ int selinux_netlbl_inode_permission(struct inode *inode, int mask)
 		release_sock(sock->sk);
 	} else
 		rc = 0;
-	up(&isec->sem);
+	mutex_unlock(&isec->lock);
 
 	return rc;
 }