From mboxrd@z Thu Jan 1 00:00:00 1970 From: PanBian Subject: Re: [PATCH] nilfs2: fix potential use after free Date: Mon, 3 Dec 2018 17:14:55 +0800 Message-ID: <20181203091455.GA9038@bp> References: <1543201709-53191-1-git-send-email-bianpan2016@163.com> <20181203.181051.1348099310050315226.konishi.ryusuke@lab.ntt.co.jp> Reply-To: PanBian Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=Qpbfx 09WsH0vUx9H/ZJVpKs7ntILqCAHmG4x4+GbK1E=; b=pulffLmJJjzQNiSl0ODUd GlelITUZbC3ZJbxi5YLcVIfTGKHvCozRVmOKeyVTk096WFEUkyn2MYxOdsF1mb8D i/OMFbyLHrY+SnbNDq5n0bepkU7PWEQDqFLTuX3wnVX8sd11x8OXiqh/y7tshx52 2tvqpqRpD/qtw+PxXqXADM= Content-Disposition: inline In-Reply-To: <20181203.181051.1348099310050315226.konishi.ryusuke@lab.ntt.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Ryusuke Konishi Cc: linux-nilfs@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Dec 03, 2018 at 06:10:51PM +0900, Ryusuke Konishi wrote: > Hi, Pan Bian > > Thank you for feeding back this patch. > I reviewed this and am thinking this must be sent to upstream. > > Did you see any kernel oops on this bug ? Not yet. In fact, I found it with a static method. Best regards, Pan Bian > > Regards, > Ryusuke Konishi > > On Mon, 26 Nov 2018 11:08:29 +0800, Pan Bian wrote: > > brelse(bh) is called to drop the reference count of bh when the call > > to nilfs_dat_translate fails. If the reference count hits 0, bh may be > > freed. However, bh->b_page is unlocked and put after that, which may > > result in a use-after-free bug. This patch moves the release operation > > after unlocking and putting the page. > > > > Signed-off-by: Pan Bian > > --- > > fs/nilfs2/gcinode.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c > > index aa3c328..a24bb29 100644 > > --- a/fs/nilfs2/gcinode.c > > +++ b/fs/nilfs2/gcinode.c > > @@ -73,10 +73,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff, > > struct the_nilfs *nilfs = inode->i_sb->s_fs_info; > > > > err = nilfs_dat_translate(nilfs->ns_dat, vbn, &pbn); > > - if (unlikely(err)) { /* -EIO, -ENOMEM, -ENOENT */ > > - brelse(bh); > > + if (unlikely(err)) /* -EIO, -ENOMEM, -ENOENT */ > > goto failed; > > - } > > } > > > > lock_buffer(bh); > > @@ -102,6 +100,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff, > > failed: > > unlock_page(bh->b_page); > > put_page(bh->b_page); > > + if (unlikely(err)) > > + brelse(bh); > > return err; > > } > > > > -- > > 2.7.4 > > > >