From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754765AbaDFXjK (ORCPT ); Sun, 6 Apr 2014 19:39:10 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59432 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754497AbaDFXjG (ORCPT ); Sun, 6 Apr 2014 19:39:06 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Linus Torvalds" , "John Sullivan" , "Theodore Ts'o" Date: Mon, 07 Apr 2014 00:35:48 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 04/18] ext4: atomically set inode->i_flags in ext4_set_inode_flags() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.2.102 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.57-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit 00a1a053ebe5febcfc2ec498bd894f035ad2aa06 upstream. Use cmpxchg() to atomically set i_flags instead of clearing out the S_IMMUTABLE, S_APPEND, etc. flags and then setting them from the EXT4_IMMUTABLE_FL, EXT4_APPEND_FL flags, since this opens up a race where an immutable file has the immutable flag cleared for a brief window of time. Reported-by: John Sullivan Signed-off-by: "Theodore Ts'o" Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- fs/ext4/inode.c | 15 +++++++++------ include/linux/bitops.h | 15 +++++++++++++++ 2 files changed, 24 insertions(+), 6 deletions(-) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -38,6 +38,7 @@ #include #include #include +#include #include "ext4_jbd2.h" #include "xattr.h" @@ -3694,18 +3695,20 @@ int ext4_get_inode_loc(struct inode *ino void ext4_set_inode_flags(struct inode *inode) { unsigned int flags = EXT4_I(inode)->i_flags; + unsigned int new_fl = 0; - inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC); if (flags & EXT4_SYNC_FL) - inode->i_flags |= S_SYNC; + new_fl |= S_SYNC; if (flags & EXT4_APPEND_FL) - inode->i_flags |= S_APPEND; + new_fl |= S_APPEND; if (flags & EXT4_IMMUTABLE_FL) - inode->i_flags |= S_IMMUTABLE; + new_fl |= S_IMMUTABLE; if (flags & EXT4_NOATIME_FL) - inode->i_flags |= S_NOATIME; + new_fl |= S_NOATIME; if (flags & EXT4_DIRSYNC_FL) - inode->i_flags |= S_DIRSYNC; + new_fl |= S_DIRSYNC; + set_mask_bits(&inode->i_flags, + S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC, new_fl); } /* Propagate flags from i_flags to EXT4_I(inode)->i_flags */ --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -168,6 +168,21 @@ static inline unsigned long __ffs64(u64 #ifdef __KERNEL__ +#ifndef set_mask_bits +#define set_mask_bits(ptr, _mask, _bits) \ +({ \ + const typeof(*ptr) mask = (_mask), bits = (_bits); \ + typeof(*ptr) old, new; \ + \ + do { \ + old = ACCESS_ONCE(*ptr); \ + new = (old & ~mask) | bits; \ + } while (cmpxchg(ptr, old, new) != old); \ + \ + new; \ +}) +#endif + #ifndef find_last_bit /** * find_last_bit - find the last set bit in a memory region