Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753499AbaBSJxY (ORCPT ); Wed, 19 Feb 2014 04:53:24 -0500 Received: from nbl-ex10-fe01.nebula.fi ([188.117.32.121]:57262 "EHLO ex10.nebula.fi" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753229AbaBSJxV (ORCPT ); Wed, 19 Feb 2014 04:53:21 -0500 Message-ID: <53047F0E.7040705@tuxera.com> Date: Wed, 19 Feb 2014 11:53:18 +0200 From: sougata santra User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Andrew Morton CC: Christoph Hellwig , , , Vyacheslav Dubeyko , Joe Perches , Alexey Khoroshilov Subject: Re: [PATCH] hfsplus: fix concurrent acess of alloc_blocks References: <1392639647.29849.11.camel@ultrabook> <20140218140642.fdc6a406f22de69bdf73e66e@linux-foundation.org> In-Reply-To: <20140218140642.fdc6a406f22de69bdf73e66e@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [194.100.106.164] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/19/2014 12:06 AM, Andrew Morton wrote: > On Mon, 17 Feb 2014 14:20:47 +0200 Sougata Santra wrote: > >> >> Concurrent access to alloc_blocks in hfsplus_inode_info is >> protected by extents_lock mutex. This patch fixes two >> instances where alloc_blocks modification was not protected >> with this lock. This fixes possible allocation bitmap >> corruption in race conditions while extending and truncating >> files. >> >> ... >> >> --- a/fs/hfsplus/extents.c >> +++ b/fs/hfsplus/extents.c >> @@ -498,11 +498,13 @@ int hfsplus_file_extend(struct inode *inode) >> goto insert_extent; >> } >> out: >> - mutex_unlock(&hip->extents_lock); >> if (!res) { >> hip->alloc_blocks += len; >> + mutex_unlock(&hip->extents_lock); >> hfsplus_mark_inode_dirty(inode, HFSPLUS_I_ALLOC_DIRTY); >> + return 0; >> } >> + mutex_unlock(&hip->extents_lock); >> return res; >> > > This looks OK. > >> @@ -592,9 +594,9 @@ void hfsplus_file_truncate(struct inode *inode) >> hfs_brec_remove(&fd); >> } >> hfs_find_exit(&fd); >> - mutex_unlock(&hip->extents_lock); >> >> hip->alloc_blocks = blk_cnt; >> + mutex_unlock(&hip->extents_lock); >> out: >> hip->phys_size = inode->i_size; >> hip->fs_blocks = (inode->i_size + sb->s_blocksize - 1) >> > > But this does not. To provide locking for > hfsplus_inode_info.alloc_blocks, we must take the lock *before* taking > a local copy of ->alloc_blocks. > > Please review: > > --- a/fs/hfsplus/extents.c~hfsplus-fix-concurrent-acess-of-alloc_blocks-fix > +++ a/fs/hfsplus/extents.c > @@ -556,11 +556,13 @@ void hfsplus_file_truncate(struct inode > > blk_cnt = (inode->i_size + HFSPLUS_SB(sb)->alloc_blksz - 1) >> > HFSPLUS_SB(sb)->alloc_blksz_shift; > + > + mutex_lock(&hip->extents_lock); > + > alloc_cnt = hip->alloc_blocks; > if (blk_cnt == alloc_cnt) > - goto out; > + goto out_unlock; > > - mutex_lock(&hip->extents_lock); > res = hfs_find_init(HFSPLUS_SB(sb)->ext_tree, &fd); > if (res) { > mutex_unlock(&hip->extents_lock); > @@ -594,6 +596,7 @@ void hfsplus_file_truncate(struct inode > hfs_find_exit(&fd); > > hip->alloc_blocks = blk_cnt; > +out_unlock: > mutex_unlock(&hip->extents_lock); > out: We can also remove this label ? > hip->phys_size = inode->i_size; > _ > -- 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/