Merge tag 'selinux-pr-20180629' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull selinux fix from Paul Moore:
 "One fairly straightforward patch to fix a longstanding issue where a
  process could stall while accessing files in selinuxfs and block
  everyone else due to a held mutex.

  The patch passes all our tests and looks to apply cleanly to your
  current tree"

* tag 'selinux-pr-20180629' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: move user accesses in selinuxfs out of locked regions

1 files changed, 33 insertions, 45 deletions

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index f3d374d2ca04..79d3709b0671 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -441,22 +441,16 @@ static int sel_release_policy(struct inode *inode, struct file *filp)
 static ssize_t sel_read_policy(struct file *filp, char __user *buf,
 			       size_t count, loff_t *ppos)
 {
-	struct selinux_fs_info *fsi = file_inode(filp)->i_sb->s_fs_info;
 	struct policy_load_memory *plm = filp->private_data;
 	int ret;
 
-	mutex_lock(&fsi->mutex);
-
 	ret = avc_has_perm(&selinux_state,
 			   current_sid(), SECINITSID_SECURITY,
 			  SECCLASS_SECURITY, SECURITY__READ_POLICY, NULL);
 	if (ret)
-		goto out;
+		return ret;
 
-	ret = simple_read_from_buffer(buf, count, ppos, plm->data, plm->len);
-out:
-	mutex_unlock(&fsi->mutex);
-	return ret;
+	return simple_read_from_buffer(buf, count, ppos, plm->data, plm->len);
 }
 
 static vm_fault_t sel_mmap_policy_fault(struct vm_fault *vmf)
@@ -1188,25 +1182,29 @@ static ssize_t sel_read_bool(struct file *filep, char __user *buf,
 	ret = -EINVAL;
 	if (index >= fsi->bool_num || strcmp(name,
 					     fsi->bool_pending_names[index]))
-		goto out;
+		goto out_unlock;
 
 	ret = -ENOMEM;
 	page = (char *)get_zeroed_page(GFP_KERNEL);
 	if (!page)
-		goto out;
+		goto out_unlock;
 
 	cur_enforcing = security_get_bool_value(fsi->state, index);
 	if (cur_enforcing < 0) {
 		ret = cur_enforcing;
-		goto out;
+		goto out_unlock;
 	}
 	length = scnprintf(page, PAGE_SIZE, "%d %d", cur_enforcing,
 			  fsi->bool_pending_values[index]);
-	ret = simple_read_from_buffer(buf, count, ppos, page, length);
-out:
 	mutex_unlock(&fsi->mutex);
+	ret = simple_read_from_buffer(buf, count, ppos, page, length);
+out_free:
 	free_page((unsigned long)page);
 	return ret;
+
+out_unlock:
+	mutex_unlock(&fsi->mutex);
+	goto out_free;
 }
 
 static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
@@ -1219,6 +1217,17 @@ static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
 	unsigned index = file_inode(filep)->i_ino & SEL_INO_MASK;
 	const char *name = filep->f_path.dentry->d_name.name;
 
+	if (count >= PAGE_SIZE)
+		return -ENOMEM;
+
+	/* No partial writes. */
+	if (*ppos != 0)
+		return -EINVAL;
+
+	page = memdup_user_nul(buf, count);
+	if (IS_ERR(page))
+		return PTR_ERR(page);
+
 	mutex_lock(&fsi->mutex);
 
 	length = avc_has_perm(&selinux_state,
@@ -1233,22 +1242,6 @@ static ssize_t sel_write_bool(struct file *filep, const char __user *buf,
 					     fsi->bool_pending_names[index]))
 		goto out;
 
-	length = -ENOMEM;
-	if (count >= PAGE_SIZE)
-		goto out;
-
-	/* No partial writes. */
-	length = -EINVAL;
-	if (*ppos != 0)
-		goto out;
-
-	page = memdup_user_nul(buf, count);
-	if (IS_ERR(page)) {
-		length = PTR_ERR(page);
-		page = NULL;
-		goto out;
-	}
-
 	length = -EINVAL;
 	if (sscanf(page, "%d", &new_value) != 1)
 		goto out;
@@ -1280,6 +1273,17 @@ static ssize_t sel_commit_bools_write(struct file *filep,
 	ssize_t length;
 	int new_value;
 
+	if (count >= PAGE_SIZE)
+		return -ENOMEM;
+
+	/* No partial writes. */
+	if (*ppos != 0)
+		return -EINVAL;
+
+	page = memdup_user_nul(buf, count);
+	if (IS_ERR(page))
+		return PTR_ERR(page);
+
 	mutex_lock(&fsi->mutex);
 
 	length = avc_has_perm(&selinux_state,
@@ -1289,22 +1293,6 @@ static ssize_t sel_commit_bools_write(struct file *filep,
 	if (length)
 		goto out;
 
-	length = -ENOMEM;
-	if (count >= PAGE_SIZE)
-		goto out;
-
-	/* No partial writes. */
-	length = -EINVAL;
-	if (*ppos != 0)
-		goto out;
-
-	page = memdup_user_nul(buf, count);
-	if (IS_ERR(page)) {
-		length = PTR_ERR(page);
-		page = NULL;
-		goto out;
-	}
-
 	length = -EINVAL;
 	if (sscanf(page, "%d", &new_value) != 1)
 		goto out;