From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 30 Oct 2016 11:52:31 +0100 From: Jan Kara To: Linus Torvalds Cc: Al Viro , Christoph Hellwig , Jan Kara , Dmitry Monakhov , Jeff Moyer , linux-fsdevel , linux-aio@kvack.org, Linux Kernel Mailing List , stable Subject: Re: [PATCH] aio: fix a user triggered use after free (and fix freeze protection of aio writes) Message-ID: <20161030105231.GA16015@quack2.suse.cz> References: <1477727070-18806-1-git-send-email-hch@lst.de> <1477727070-18806-2-git-send-email-hch@lst.de> <20161029122451.GQ19539@ZenIV.linux.org.uk> <20161029152017.GA7388@lst.de> <20161029185222.GT19539@ZenIV.linux.org.uk> <20161029191753.GU19539@ZenIV.linux.org.uk> <20161030094437.GA3225@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161030094437.GA3225@quack2.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sun 30-10-16 10:44:37, Jan Kara wrote: > On Sat 29-10-16 13:09:25, Linus Torvalds wrote: > > On Sat, Oct 29, 2016 at 12:17 PM, Al Viro wrote: > > > > > > AFAICS, the possibility of dropping the last reference to struct file > > > before ->write_iter() has returned is fundamentally broken. I might be > > > missing something subtle here, but... > > > > Ok, let's add a get_file(); fput(); around that whole iter call sequence. > > > > And that's a separate issue from "we should hold the fs freezer lock > > around the whole operation". So I think we need both. > > Yup, these are two separate issues. I'm fine with adding get_file(); fput() > around the iter call sequence. Then, when we have struct file available for > the whole time ->write_iter runs, I'd prefer to keep the call to fool > lockdep where original file_end_write() call was - that gives us proper > lockdep coverage for all the code behind iter_op(). The downside is we > cannot keep helpers as elegant as you suggested in your patch but I believe > it's bearable and worth the additional lockdep coverage. I'll send patches > shortly... Hum, the additional refcount patch oopses on me when running generic/323, I'll have to board to my flight to US shortly so I won't be able to send it soon - maybe when I'm transferring in Denver ;). Honza -- Jan Kara SUSE Labs, CR