Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753566AbbEBTMA (ORCPT ); Sat, 2 May 2015 15:12:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44495 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753548AbbEBTLy (ORCPT ); Sat, 2 May 2015 15:11:54 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Meddaugh , Andrew Elble , Al Viro Subject: [PATCH 4.0 064/220] NFS: fix BUG() crash in notify_change() with patch to chown_common() Date: Sat, 2 May 2015 20:59:39 +0200 Message-Id: <20150502185857.140316883@linuxfoundation.org> X-Mailer: git-send-email 2.3.7 In-Reply-To: <20150502185854.333748961@linuxfoundation.org> References: <20150502185854.333748961@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2805 Lines: 72 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrew Elble commit c1b8940b42bb6487b10f2267a96b486276ce9ff7 upstream. We have observed a BUG() crash in fs/attr.c:notify_change(). The crash occurs during an rsync into a filesystem that is exported via NFS. 1.) fs/attr.c:notify_change() modifies the caller's version of attr. 2.) 6de0ec00ba8d ("VFS: make notify_change pass ATTR_KILL_S*ID to setattr operations") introduced a BUG() restriction such that "no function will ever call notify_change() with both ATTR_MODE and ATTR_KILL_S*ID set". Under some circumstances though, it will have assisted in setting the caller's version of attr to this very combination. 3.) 27ac0ffeac80 ("locks: break delegations on any attribute modification") introduced code to handle breaking delegations. This can result in notify_change() being re-called. attr _must_ be explicitly reset to avoid triggering the BUG() established in #2. 4.) The path that that triggers this is via fs/open.c:chmod_common(). The combination of attr flags set here and in the first call to notify_change() along with a later failed break_deleg_wait() results in notify_change() being called again via retry_deleg without resetting attr. Solution is to move retry_deleg in chmod_common() a bit further up to ensure attr is completely reset. There are other places where this seemingly could occur, such as fs/utimes.c:utimes_common(), but the attr flags are not initially set in such a way to trigger this. Fixes: 27ac0ffeac80 ("locks: break delegations on any attribute modification") Reported-by: Eric Meddaugh Tested-by: Eric Meddaugh Signed-off-by: Andrew Elble Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/open.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/open.c +++ b/fs/open.c @@ -570,6 +570,7 @@ static int chown_common(struct path *pat uid = make_kuid(current_user_ns(), user); gid = make_kgid(current_user_ns(), group); +retry_deleg: newattrs.ia_valid = ATTR_CTIME; if (user != (uid_t) -1) { if (!uid_valid(uid)) @@ -586,7 +587,6 @@ static int chown_common(struct path *pat if (!S_ISDIR(inode->i_mode)) newattrs.ia_valid |= ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV; -retry_deleg: mutex_lock(&inode->i_mutex); error = security_path_chown(path, uid, gid); if (!error) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/