ovl: perform vfs_getxattr() with mounter creds

[ Upstream commit 554677b97257b0b69378bd74e521edb7e94769ff ]

The vfs_getxattr() in ovl_xattr_set() is used to check whether an xattr
exist on a lower layer file that is to be removed.  If the xattr does not
exist, then no need to copy up the file.

This call of vfs_getxattr() wasn't wrapped in credential override, and this
is probably okay.  But for consitency wrap this instance as well.

Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 30a1c7fc8c75c1b14d7f33babdebc655a6fa429d..ac6efac119fb92804e077b4e954c93a7d6e6454d 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -216,7 +216,9 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
                goto out;
 
        if (!value && !upperdentry) {
+               old_cred = ovl_override_creds(dentry->d_sb);
                err = vfs_getxattr(realdentry, name, NULL, 0);
+               revert_creds(old_cred);
                if (err < 0)
                        goto out_drop_write;
        }