From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nautica.notk.org ([91.121.71.147]:40467 "EHLO nautica.notk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389570AbeHAQY6 (ORCPT ); Wed, 1 Aug 2018 12:24:58 -0400 Date: Wed, 1 Aug 2018 16:38:40 +0200 From: Dominique Martinet To: Greg Kurz Cc: v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, Matthew Wilcox , linux-kernel@vger.kernel.org Subject: Re: [V9fs-developer] [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs Message-ID: <20180801143840.GA21463@nautica> References: <20180730093101.GA7894@nautica> <1532943263-24378-1-git-send-email-asmadeus@codewreck.org> <20180801161413.0523a821@bahia.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180801161413.0523a821@bahia.lan> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Greg Kurz wrote on Wed, Aug 01, 2018: > > @@ -263,13 +261,13 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size) > > if (!req) > > return NULL; > > > > - req->tc = p9_fcall_alloc(alloc_msize); > > - req->rc = p9_fcall_alloc(alloc_msize); > > - if (!req->tc || !req->rc) > > + if (p9_fcall_alloc(&req->tc, alloc_msize)) > > + goto free; > > + if (p9_fcall_alloc(&req->rc, alloc_msize)) > > goto free; > > Hmm... if the first allocation fails, we will kfree() req->rc.sdata. > > Are we sure we won't have a stale pointer or uninitialized data in > there ? Yeah, Jun pointed that out and I have a v2 that only frees as needed with an extra goto (I sent an incremental diff in my reply to his comment here[1]) [1] https://lkml.kernel.org/r/20180731011256.GA30388@nautica > And even if we don't with the current code base, this is fragile and > could be easily broken. > > I think you should drop this hunk and rather rename p9_fcall_alloc() to > p9_fcall_alloc_sdata() instead, since this is what the function is > actually doing with this patch applied. Hmm. I agree the naming isn't accurate, but even if we rename it we'll need to pass a pointer to fcall as argument as it inits its capacity. p9_fcall_init(fc, msize) might be simpler? (I'm not sure I follow what you mean by 'drop this hunk', to be honest, did you want a single function call to init both maybe?) -- Dominique