Commit a02cd680 authored by Stephen Smalley's avatar Stephen Smalley Committed by Paul Moore
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selinux: allow multiple opens of /sys/fs/selinux/policy 

Currently there can only be a single open of /sys/fs/selinux/policy at
any time. This allows any process to block any other process from
reading the kernel policy. The original motivation seems to have been
a mix of preventing an inconsistent view of the policy size and
preventing userspace from allocating kernel memory without bound, but
this is arguably equally bad. Eliminate the policy_opened flag and
shrink the critical section that the policy mutex is held. While we
are making changes here, drop a couple of extraneous BUG_ONs.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/selinux/20100726193414.19538.64028.stgit@paris.rdu.redhat.com/


Signed-off-by: default avatarStephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent ad1ac3d7

security/selinux/selinuxfs.c

+4 −23
Original line number Diff line number Diff line
@@ -76,7 +76,6 @@ struct selinux_fs_info { 
	int *bool_pending_values;

	struct dentry *class_dir;

	unsigned long last_class_ino;

	bool policy_opened;

	unsigned long last_ino;

	struct super_block *sb;

};
@@ -340,44 +339,31 @@ struct policy_load_memory { 


static int sel_open_policy(struct inode *inode, struct file *filp)

{

	struct selinux_fs_info *fsi = inode->i_sb->s_fs_info;

	struct policy_load_memory *plm = NULL;

	int rc;



	BUG_ON(filp->private_data);



	mutex_lock(&selinux_state.policy_mutex);



	rc = avc_has_perm(current_sid(), SECINITSID_SECURITY,

			  SECCLASS_SECURITY, SECURITY__READ_POLICY, NULL);

	if (rc)

		goto err;



	rc = -EBUSY;

	if (fsi->policy_opened)

		goto err;

		return rc;



	rc = -ENOMEM;

	plm = kzalloc_obj(*plm);

	if (!plm)

		goto err;

		return -ENOMEM;



	mutex_lock(&selinux_state.policy_mutex);

	rc = security_read_policy(&plm->data, &plm->len);

	if (rc)

		goto err;



	if ((size_t)i_size_read(inode) != plm->len) {

		inode_lock(inode);

		i_size_write(inode, plm->len);

		inode_unlock(inode);

	}



	fsi->policy_opened = 1;

	mutex_unlock(&selinux_state.policy_mutex);



	filp->private_data = plm;



	mutex_unlock(&selinux_state.policy_mutex);



	return 0;

err:

	mutex_unlock(&selinux_state.policy_mutex);
@@ -390,13 +376,8 @@ static int sel_open_policy(struct inode *inode, struct file *filp) 


static int sel_release_policy(struct inode *inode, struct file *filp)

{

	struct selinux_fs_info *fsi = inode->i_sb->s_fs_info;

	struct policy_load_memory *plm = filp->private_data;



	BUG_ON(!plm);



	fsi->policy_opened = 0;



	vfree(plm->data);

	kfree(plm);