From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaegeuk Kim Subject: Re: [f2fs-dev][PATCH 1/2] f2fs: check name_len of dir entry to prevent from deadloop Date: Fri, 4 Jul 2014 23:43:13 -0700 Message-ID: <20140705064313.GA35795@jmac.local> References: <000001cf95b5$eac71ad0$c0555070$@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Changman Lee , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Chao Yu Return-path: Content-Disposition: inline In-Reply-To: <000001cf95b5$eac71ad0$c0555070$@samsung.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi Chao, On Wed, Jul 02, 2014 at 01:23:47PM +0800, Chao Yu wrote: > We assume that modification of some special application could result in zeroed > name_len, or it is consciously made by somebody. We will deadloop in > find_in_block when name_len of dir entry is zero. Could you explain this a little bit more? I'm not sure how it can happen. I think the zeroed name_len would cause some problems in f2fs_add_link. Thanks, > > This patch is added for preventing deadloop in above scenario. > > Signed-off-by: Chao Yu > --- > fs/f2fs/dir.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index be8c7af..4316ec5 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -121,6 +121,16 @@ static struct f2fs_dir_entry *find_in_block(struct page *dentry_page, > } > } > > + /* check name_len to prevent from deadloop here */ > + if (unlikely(de->name_len == 0)) { > + struct inode *inode = dentry_page->mapping->host; > + > + f2fs_msg(inode->i_sb, KERN_ERR, > + "zero-length dir entry, ino = %lu, name = %s", > + (unsigned long)inode->i_ino, name->name); > + break; > + } > + > bit_start = bit_pos > + GET_DENTRY_SLOTS(le16_to_cpu(de->name_len)); > } > -- > 1.7.9.5 -- Jaegeuk Kim