From: Miklos Szeredi <mszeredi@redhat.com>
Date: Mon, 29 May 2017 13:15:27 +0000 (+0200)
Subject: ovl: filter trusted xattr for non-admin
X-Git-Tag: v4.1.52~225
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=208325ef13eb870650640cb2df4a8f3cd990ff9c;p=thirdparty%2Fkernel%2Fstable.git

ovl: filter trusted xattr for non-admin

[ Upstream commit a082c6f680da298cf075886ff032f32ccb7c5e1a ]

Filesystems filter out extended attributes in the "trusted." domain for
unprivlieged callers.

Overlay calls underlying filesystem's method with elevated privs, so need
to do the filtering in overlayfs too.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index d293034ae2cb3..e73f0070a0fc8 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -274,6 +274,16 @@ ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
 	return vfs_getxattr(realpath.dentry, name, value, size);
 }
 
+static bool ovl_can_list(const char *s)
+{
+	/* List all non-trusted xatts */
+	if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
+		return true;
+
+	/* Never list trusted.overlay, list other trusted for superuser only */
+	return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
+}
+
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 {
 	struct path realpath;
@@ -298,7 +308,7 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 			return -EIO;
 
 		len -= slen;
-		if (ovl_is_private_xattr(s)) {
+		if (!ovl_can_list(s)) {
 			res -= slen;
 			memmove(s, s + slen, len);
 		} else {