Commit 9287aed2 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher Committed by Paul Moore
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selinux: Convert isec->lock into a spinlock 



Convert isec->lock from a mutex into a spinlock.  Instead of holding
the lock while sleeping in inode_doinit_with_dentry, set
isec->initialized to LABEL_PENDING and release the lock.  Then, when
the sid has been determined, re-acquire the lock.  If isec->initialized
is still set to LABEL_PENDING, set isec->sid; otherwise, the sid has
been set by another task (LABEL_INITIALIZED) or invalidated
(LABEL_INVALID) in the meantime.

This fixes a deadlock on gfs2 where

 * one task is in inode_doinit_with_dentry -> gfs2_getxattr, holds
   isec->lock, and tries to acquire the inode's glock, and

 * another task is in do_xmote -> inode_go_inval ->
   selinux_inode_invalidate_secctx, holds the inode's glock, and
   tries to acquire isec->lock.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
[PM: minor tweaks to keep checkpatch.pl happy]
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent 3322d0d6

security/selinux/hooks.c

+63 −38
Original line number Diff line number Diff line
@@ -231,7 +231,7 @@ static int inode_alloc_security(struct inode *inode) 
	if (!isec)

		return -ENOMEM;



	mutex_init(&isec->lock);

	spin_lock_init(&isec->lock);

	INIT_LIST_HEAD(&isec->list);

	isec->inode = inode;

	isec->sid = SECINITSID_UNLABELED;
@@ -1382,7 +1382,8 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
{

	struct superblock_security_struct *sbsec = NULL;

	struct inode_security_struct *isec = inode->i_security;

	u32 sid;

	u32 task_sid, sid = 0;

	u16 sclass;

	struct dentry *dentry;

#define INITCONTEXTLEN 255

	char *context = NULL;
@@ -1392,7 +1393,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
	if (isec->initialized == LABEL_INITIALIZED)

		return 0;



	mutex_lock(&isec->lock);

	spin_lock(&isec->lock);

	if (isec->initialized == LABEL_INITIALIZED)

		goto out_unlock;
@@ -1411,12 +1412,18 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
		goto out_unlock;

	}



	sclass = isec->sclass;

	task_sid = isec->task_sid;

	sid = isec->sid;

	isec->initialized = LABEL_PENDING;

	spin_unlock(&isec->lock);



	switch (sbsec->behavior) {

	case SECURITY_FS_USE_NATIVE:

		break;

	case SECURITY_FS_USE_XATTR:

		if (!(inode->i_opflags & IOP_XATTR)) {

			isec->sid = sbsec->def_sid;

			sid = sbsec->def_sid;

			break;

		}

		/* Need a dentry, since the xattr API requires one.
@@ -1438,7 +1445,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
			 * inode_doinit with a dentry, before these inodes could

			 * be used again by userspace.

			 */

			goto out_unlock;

			goto out;

		}



		len = INITCONTEXTLEN;
@@ -1446,7 +1453,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
		if (!context) {

			rc = -ENOMEM;

			dput(dentry);

			goto out_unlock;

			goto out;

		}

		context[len] = '\0';

		rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
@@ -1457,14 +1464,14 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
			rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);

			if (rc < 0) {

				dput(dentry);

				goto out_unlock;

				goto out;

			}

			len = rc;

			context = kmalloc(len+1, GFP_NOFS);

			if (!context) {

				rc = -ENOMEM;

				dput(dentry);

				goto out_unlock;

				goto out;

			}

			context[len] = '\0';

			rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
@@ -1476,7 +1483,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
				       "%d for dev=%s ino=%ld\n", __func__,

				       -rc, inode->i_sb->s_id, inode->i_ino);

				kfree(context);

				goto out_unlock;

				goto out;

			}

			/* Map ENODATA to the default file SID */

			sid = sbsec->def_sid;
@@ -1506,28 +1513,25 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
			}

		}

		kfree(context);

		isec->sid = sid;

		break;

	case SECURITY_FS_USE_TASK:

		isec->sid = isec->task_sid;

		sid = task_sid;

		break;

	case SECURITY_FS_USE_TRANS:

		/* Default to the fs SID. */

		isec->sid = sbsec->sid;

		sid = sbsec->sid;



		/* Try to obtain a transition SID. */

		rc = security_transition_sid(isec->task_sid, sbsec->sid,

					     isec->sclass, NULL, &sid);

		rc = security_transition_sid(task_sid, sid, sclass, NULL, &sid);

		if (rc)

			goto out_unlock;

		isec->sid = sid;

			goto out;

		break;

	case SECURITY_FS_USE_MNTPOINT:

		isec->sid = sbsec->mntpoint_sid;

		sid = sbsec->mntpoint_sid;

		break;

	default:

		/* Default to the fs superblock SID. */

		isec->sid = sbsec->sid;

		sid = sbsec->sid;



		if ((sbsec->flags & SE_SBGENFS) && !S_ISLNK(inode->i_mode)) {

			/* We must have a dentry to determine the label on
@@ -1550,21 +1554,30 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent 
			 * could be used again by userspace.

			 */

			if (!dentry)

				goto out_unlock;

			rc = selinux_genfs_get_sid(dentry, isec->sclass,

				goto out;

			rc = selinux_genfs_get_sid(dentry, sclass,

						   sbsec->flags, &sid);

			dput(dentry);

			if (rc)

				goto out_unlock;

			isec->sid = sid;

				goto out;

		}

		break;

	}



out:

	spin_lock(&isec->lock);

	if (isec->initialized == LABEL_PENDING) {

		if (!sid || rc) {

			isec->initialized = LABEL_INVALID;

			goto out_unlock;

		}



		isec->initialized = LABEL_INITIALIZED;

		isec->sid = sid;

	}



out_unlock:

	mutex_unlock(&isec->lock);

	spin_unlock(&isec->lock);

	return rc;

}
@@ -3195,9 +3208,11 @@ static void selinux_inode_post_setxattr(struct dentry *dentry, const char *name, 
	}



	isec = backing_inode_security(dentry);

	spin_lock(&isec->lock);

	isec->sclass = inode_mode_to_security_class(inode->i_mode);

	isec->sid = newsid;

	isec->initialized = LABEL_INITIALIZED;

	spin_unlock(&isec->lock);



	return;

}
@@ -3290,9 +3305,11 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name, 
	if (rc)

		return rc;



	spin_lock(&isec->lock);

	isec->sclass = inode_mode_to_security_class(inode->i_mode);

	isec->sid = newsid;

	isec->initialized = LABEL_INITIALIZED;

	spin_unlock(&isec->lock);

	return 0;

}
@@ -3953,9 +3970,11 @@ static void selinux_task_to_inode(struct task_struct *p, 
	struct inode_security_struct *isec = inode->i_security;

	u32 sid = task_sid(p);



	spin_lock(&isec->lock);

	isec->sclass = inode_mode_to_security_class(inode->i_mode);

	isec->sid = sid;

	isec->initialized = LABEL_INITIALIZED;

	spin_unlock(&isec->lock);

}



/* Returns error only if unable to parse addresses */
@@ -4274,24 +4293,24 @@ static int selinux_socket_post_create(struct socket *sock, int family, 
	const struct task_security_struct *tsec = current_security();

	struct inode_security_struct *isec = inode_security_novalidate(SOCK_INODE(sock));

	struct sk_security_struct *sksec;

	u16 sclass = socket_type_to_security_class(family, type, protocol);

	u32 sid = SECINITSID_KERNEL;

	int err = 0;



	isec->sclass = socket_type_to_security_class(family, type, protocol);



	if (kern)

		isec->sid = SECINITSID_KERNEL;

	else {

		err = socket_sockcreate_sid(tsec, isec->sclass, &(isec->sid));

	if (!kern) {

		err = socket_sockcreate_sid(tsec, sclass, &sid);

		if (err)

			return err;

	}



	isec->sclass = sclass;

	isec->sid = sid;

	isec->initialized = LABEL_INITIALIZED;



	if (sock->sk) {

		sksec = sock->sk->sk_security;

		sksec->sid = isec->sid;

		sksec->sclass = isec->sclass;

		sksec->sclass = sclass;

		sksec->sid = sid;

		err = selinux_netlbl_socket_post_create(sock->sk, family);

	}
@@ -4467,16 +4486,22 @@ static int selinux_socket_accept(struct socket *sock, struct socket *newsock) 
	int err;

	struct inode_security_struct *isec;

	struct inode_security_struct *newisec;

	u16 sclass;

	u32 sid;



	err = sock_has_perm(current, sock->sk, SOCKET__ACCEPT);

	if (err)

		return err;



	newisec = inode_security_novalidate(SOCK_INODE(newsock));



	isec = inode_security_novalidate(SOCK_INODE(sock));

	newisec->sclass = isec->sclass;

	newisec->sid = isec->sid;

	spin_lock(&isec->lock);

	sclass = isec->sclass;

	sid = isec->sid;

	spin_unlock(&isec->lock);



	newisec = inode_security_novalidate(SOCK_INODE(newsock));

	newisec->sclass = sclass;

	newisec->sid = sid;

	newisec->initialized = LABEL_INITIALIZED;



	return 0;
@@ -5979,9 +6004,9 @@ static void selinux_inode_invalidate_secctx(struct inode *inode) 
{

	struct inode_security_struct *isec = inode->i_security;



	mutex_lock(&isec->lock);

	spin_lock(&isec->lock);

	isec->initialized = LABEL_INVALID;

	mutex_unlock(&isec->lock);

	spin_unlock(&isec->lock);

}



/*

security/selinux/include/objsec.h

+3 −2
Original line number Diff line number Diff line
@@ -39,7 +39,8 @@ struct task_security_struct { 


enum label_initialized {

	LABEL_INVALID,		/* invalid or not initialized */

	LABEL_INITIALIZED	/* initialized */

	LABEL_INITIALIZED,	/* initialized */

	LABEL_PENDING

};



struct inode_security_struct {
@@ -52,7 +53,7 @@ struct inode_security_struct { 
	u32 sid;		/* SID of this object */

	u16 sclass;		/* security class of this object */

	unsigned char initialized;	/* initialization flag */

	struct mutex lock;

	spinlock_t lock;

};



struct file_security_struct {

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