From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1972EB64DC for ; Sun, 9 Jul 2023 19:49:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229441AbjGITtC (ORCPT ); Sun, 9 Jul 2023 15:49:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229779AbjGITs7 (ORCPT ); Sun, 9 Jul 2023 15:48:59 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F3CA131 for ; Sun, 9 Jul 2023 12:48:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 20CCA60C38 for ; Sun, 9 Jul 2023 19:48:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A26EC433C8; Sun, 9 Jul 2023 19:48:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1688932131; bh=i+XOnoxVNlDAYmcA+gZO9/oFEjVljgF6LZpweWKnr+4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1bpZN40vT5i7wmGhmqz7JWepM/gLgfn1eoKIgbVWHW8U7bkYWItAkicyQCpIox1NR tmdgeY4ROodxB75iDdkQRQV4NGbdpNhxZKoW6mNYs9JihDGhqaPA9KtuumxKEDI+yI t4fJbs7bpW6eIRdxHYK9PkIlWc2DRWNCDL7WZUbY= Date: Sun, 9 Jul 2023 18:09:53 +0200 From: Greg Kroah-Hartman To: Suren Baghdasaryan Cc: Thorsten Leemhuis , stable@vger.kernel.org, patches@lists.linux.dev, David Hildenbrand , Jiri Slaby , Holger =?iso-8859-1?Q?Hoffst=E4tte?= , Jacob Young , "Liam R. Howlett" , Andrew Morton Subject: Re: [PATCH 6.4 7/8] fork: lock VMAs of the parent process when forking Message-ID: <2023070931-conjuror-dweeb-bb4b@gregkh> References: <20230709111345.297026264@linuxfoundation.org> <20230709111345.516444847@linuxfoundation.org> <2023070904-customer-concise-e6fe@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sun, Jul 09, 2023 at 09:04:09AM -0700, Suren Baghdasaryan wrote: > On Sun, Jul 9, 2023 at 6:32 AM Greg Kroah-Hartman > wrote: > > > > On Sun, Jul 09, 2023 at 02:39:00PM +0200, Thorsten Leemhuis wrote: > > > On 09.07.23 13:14, Greg Kroah-Hartman wrote: > > > > From: Suren Baghdasaryan > > > > > > > > commit 2b4f3b4987b56365b981f44a7e843efa5b6619b9 upstream. > > > > > > > > Patch series "Avoid memory corruption caused by per-VMA locks", v4. > > > > > > > > A memory corruption was reported in [1] with bisection pointing to the > > > > patch [2] enabling per-VMA locks for x86. Based on the reproducer > > > > provided in [1] we suspect this is caused by the lack of VMA locking while > > > > forking a child process. > > > > [...] > > > > > > Question from someone that is neither a C nor a git expert -- and thus > > > might say something totally stupid below (and thus maybe should not have > > > sent this mail at all). > > > > > > But I have to wonder: is adding this patch to stable necessary given > > > patch 8/8? > > > > > > FWIW, this change looks like this: > > > > > > > --- > > > > kernel/fork.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > --- a/kernel/fork.c > > > > +++ b/kernel/fork.c > > > > @@ -662,6 +662,12 @@ static __latent_entropy int dup_mmap(str > > > > retval = -EINTR; > > > > goto fail_uprobe_end; > > > > } > > > > +#ifdef CONFIG_PER_VMA_LOCK > > > > + /* Disallow any page faults before calling flush_cache_dup_mm */ > > > > + for_each_vma(old_vmi, mpnt) > > > > + vma_start_write(mpnt); > > > > + vma_iter_set(&old_vmi, 0); > > > > +#endif > > > > flush_cache_dup_mm(oldmm); > > > > uprobe_dup_mmap(oldmm, mm); > > > > /* > > > > > > But when I look at kernel/fork.c in mainline I can't see this bit. I > > > also only see Linus' change (e.g. patch 8/8 in this series) when I look at > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/kernel/fork.c > > > > Look at 946c6b59c56d ("Merge tag 'mm-hotfixes-stable-2023-07-08-10-43' > > of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") > > > > Where Linus manually dropped those #ifdefs. > > > > Hm, I'll leave them for now in 6.4.y as that is "safer", but if Suren > > feels comfortable, I'll gladly take a patch from him to drop them in the > > 6.4.y tree as well. > > Hi Greg, > Give me a couple hours to get back to my computer. Linus took a > different version of this patch and changed the description quite a > bit. Once I'm home I can send you the patchset that was merged into > his tree. Also let me know if you want to disable CONFIG_PER_VMA_LOCK > in the stable branch (the patch called "[PATCH 6.4 1/8] mm: disable > CONFIG_PER_VMA_LOCK until its fixed" which Linus did not take AFAIKT). No rush, you can do this on Monday. I took the patches that Linus added to his tree already into the stable 6.4.y tree, and it's in the -rc release I pushed out a few hours ago. So if you want to look at the -rc release, that would be great, the full list of patches can be seen here: https://lore.kernel.org/r/20230709111345.297026264@linuxfoundation.org thanks, greg k-h