ovl: filter trusted xattr for non-admin

a082c6f6 · Miklos Szeredi <[email protected]> · 2017-05-29 15:15:27 +02:00

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 <[email protected]>

Commit: a082c6f680da298cf075886ff032f32ccb7c5e1a
Parents: f3a15685

Changes

1 files changed · +11 −1

File	Status	Add	Del	Content
fs/overlayfs/inode.c	modified	+11	−1	View file

fs/overlayfs/inode.c

View file

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index ad9547f..d613e2c 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -240,6 +240,16 @@ 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);
@@ -263,7 +273,7 @@ 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 {