eCryptfs: fix a couple type promotion bugs

ECRYPTFS_SIZE_AND_MARKER_BYTES is type size_t, so if "rc" is negative
that gets type promoted to a high positive value and treated as success.

Fixes: 778aeb42 ("eCryptfs: Cleanup and optimize ecryptfs_lookup_interpose()")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[tyhicks: Use "if/else if" rather than "if/if"]
Cc: stable@vger.kernel.org
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

fs/ecryptfs/crypto.c

@@ -1018,8 +1018,10 @@ int ecryptfs_read_and_validate_header_region(struct inode *inode)
 
 	rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
 				 inode);
-	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
-		return rc >= 0 ? -EINVAL : rc;
+	if (rc < 0)
+		return rc;
+	else if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
+		return -EINVAL;
 	rc = ecryptfs_validate_marker(marker);
 	if (!rc)
 		ecryptfs_i_size_init(file_size, inode);
@@ -1381,8 +1383,10 @@ int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
 				     ecryptfs_inode_to_lower(inode),
 				     ECRYPTFS_XATTR_NAME, file_size,
 				     ECRYPTFS_SIZE_AND_MARKER_BYTES);
-	if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
-		return rc >= 0 ? -EINVAL : rc;
+	if (rc < 0)
+		return rc;
+	else if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
+		return -EINVAL;
 	rc = ecryptfs_validate_marker(marker);
 	if (!rc)
 		ecryptfs_i_size_init(file_size, inode);