From 29f5b648fa0b31ad614c78468b9279e5fa96397a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?=
 <emulatorman@parabola.nu>
Date: Fri, 11 Nov 2016 16:22:27 -0300
Subject: Linux-libre 4.8.7-gnu

---
 fs/overlayfs/super.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'fs/overlayfs/super.c')

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e2a94a267..a78415d77 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1026,6 +1026,21 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 
 	posix_acl_release(acl);
 
+	/*
+	 * Check if sgid bit needs to be cleared (actual setacl operation will
+	 * be done with mounter's capabilities and so that won't do it for us).
+	 */
+	if (unlikely(inode->i_mode & S_ISGID) &&
+	    handler->flags == ACL_TYPE_ACCESS &&
+	    !in_group_p(inode->i_gid) &&
+	    !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
+		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+		err = ovl_setattr(dentry, &iattr);
+		if (err)
+			return err;
+	}
+
 	err = ovl_xattr_set(dentry, handler->name, value, size, flags);
 	if (!err)
 		ovl_copyattr(ovl_inode_real(inode, NULL), inode);
-- 
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