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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 7fb53d05553780ac4bc9f3909afdb81df723af32..16f6db88c8e5c067515d8a39f186414fe49d153c 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -227,6 +227,16 @@ int ovl_xattr_get(struct dentry *dentry, const char *name,
        return res;
 }
 
+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 dentry *realdentry = ovl_dentry_real(dentry);
@@ -250,7 +260,7 @@ 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 {