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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 593BAC43441 for ; Thu, 22 Nov 2018 23:09:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01A8620818 for ; Thu, 22 Nov 2018 23:09:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="e1Effspf" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01A8620818 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=joelfernandes.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392559AbeKWJuu (ORCPT ); Fri, 23 Nov 2018 04:50:50 -0500 Received: from mail-pl1-f194.google.com ([209.85.214.194]:37359 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731444AbeKWJut (ORCPT ); Fri, 23 Nov 2018 04:50:49 -0500 Received: by mail-pl1-f194.google.com with SMTP id b5so9795133plr.4 for ; Thu, 22 Nov 2018 15:09:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=9AAcwSETEnz0ffX8XhpMxl7g2fG/fKhLppB+2Cd8nXY=; b=e1EffspfsSUx/fSISq+LMgmRZYpRtMo3L2ae8L0+rP2Jc38zm3U5fB6Sd0WIZp03tw ZVoC2lpu/rLZwjvZhjPy3BxnEcLFibdh47167fwkPfvep3TQzG5XCnnvsKFrPOdkXE6I Q0amMv2B/6c+yPtj+Ire/9BlX6a8ZS6TBaFAU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=9AAcwSETEnz0ffX8XhpMxl7g2fG/fKhLppB+2Cd8nXY=; b=Wt27ahY3gZFwaoc0vbwwvMS3VG6ZOU9b04oisazsLLmO3fsfM67vA+jJDA3x7fsJ2d mGhzOePNVxN15k9rLNL0Gj5olQZRmECqozszecFbtmoFH+LZGxajgrGumoQBFy9CoDbM ZPIOxcOUYK4QT05Gdmy4CII1JW7/1t3XZsYdNm2FGhZzN68aUFr9ghvuSkO59WgU1tHD clPtU1w+KDfgLkSgRFuTOHEBLLsX+C0SWfyNZj5lZs6PuR50bxyJgOyvPHERJpa6IJ9B e4Hq+jPQAtBiJnwqhqwLEOQuDhm6Fip0EVg8lmPrJqHpmG4j+aZEgxeNJJWcDYCi3WLs PMBw== X-Gm-Message-State: AA+aEWaGsald6C8XKF1rXjktwd0JtNTh3DbMPfTb0QMb/2vEW6Kq/5Lb fEudVupgHWdFsvvtovARSxFMCw== X-Google-Smtp-Source: AFSGD/XoIyItf+SW5NLYBQ7ZwFY+fD0nlSf3rp2wSJ8noFTPHK1Bpqj4Fj1IrT7xPxOvChDi5qE8BA== X-Received: by 2002:a17:902:20c6:: with SMTP id v6mr12650647plg.156.1542928148980; Thu, 22 Nov 2018 15:09:08 -0800 (PST) Received: from localhost ([2620:0:1000:1601:3aef:314f:b9ea:889f]) by smtp.gmail.com with ESMTPSA id f6sm25619514pfg.188.2018.11.22.15.09.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 22 Nov 2018 15:09:07 -0800 (PST) Date: Thu, 22 Nov 2018 15:09:06 -0800 From: Joel Fernandes To: Andy Lutomirski Cc: Andrew Morton , Stephen Rothwell , LKML , Hugh Dickins , Jann Horn , Khalid Aziz , Linux API , "open list:KERNEL SELFTEST FRAMEWORK" , Linux-MM , marcandre.lureau@redhat.com, Matthew Wilcox , Mike Kravetz , Shuah Khan Subject: Re: [PATCH -next 1/2] mm/memfd: make F_SEAL_FUTURE_WRITE seal more robust Message-ID: <20181122230906.GA198127@google.com> References: <20181120052137.74317-1-joel@joelfernandes.org> <20181120183926.GA124387@google.com> <20181121070658.011d576d@canb.auug.org.au> <469B80CB-D982-4802-A81D-95AC493D7E87@amacapital.net> <20181120204710.GB22801@google.com> <20181120211335.GC22801@google.com> <20181121182701.0d8a775fda6af1f8d2be8f25@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 21, 2018 at 07:25:26PM -0800, Andy Lutomirski wrote: > On Wed, Nov 21, 2018 at 6:27 PM Andrew Morton wrote: > > > > On Tue, 20 Nov 2018 13:13:35 -0800 Joel Fernandes wrote: > > > > > > > I am Ok with whatever Andrew wants to do, if it is better to squash it with > > > > > the original, then I can do that and send another patch. > > > > > > > > > > > > > > > > > > From experience, Andrew will food in fixups on request :) > > > > > > Andrew, could you squash this patch into the one titled ("mm: Add an > > > F_SEAL_FUTURE_WRITE seal to memfd")? > > > > Sure. > > > > I could of course queue them separately but I rarely do so - I don't > > think that the intermediate development states are useful in the > > infinite-term, and I make them available via additional Link: tags in > > the changelog footers anyway. > > > > I think that the magnitude of these patches is such that John Stultz's > > Reviewed-by is invalidated, so this series is now in the "unreviewed" > > state. > > > > So can we have a re-review please? For convenience, here's the > > folded-together [1/1] patch, as it will go to Linus. Sure, I removed the old tags and also provide an updated patch below inline. > > From: "Joel Fernandes (Google)" > > Subject: mm: Add an F_SEAL_FUTURE_WRITE seal to memfd > > > > Android uses ashmem for sharing memory regions. We are looking forward to > > migrating all usecases of ashmem to memfd so that we can possibly remove > > the ashmem driver in the future from staging while also benefiting from > > using memfd and contributing to it. Note staging drivers are also not ABI > > and generally can be removed at anytime. [...] > > --- a/include/uapi/linux/fcntl.h~mm-add-an-f_seal_future_write-seal-to-memfd > > +++ a/include/uapi/linux/fcntl.h > > @@ -41,6 +41,7 @@ > > #define F_SEAL_SHRINK 0x0002 /* prevent file from shrinking */ > > #define F_SEAL_GROW 0x0004 /* prevent file from growing */ > > #define F_SEAL_WRITE 0x0008 /* prevent writes */ > > +#define F_SEAL_FUTURE_WRITE 0x0010 /* prevent future writes while mapped */ > > /* (1U << 31) is reserved for signed error codes */ > > > > /* > > --- a/mm/memfd.c~mm-add-an-f_seal_future_write-seal-to-memfd > > +++ a/mm/memfd.c > > @@ -131,7 +131,8 @@ static unsigned int *memfd_file_seals_pt > > #define F_ALL_SEALS (F_SEAL_SEAL | \ > > F_SEAL_SHRINK | \ > > F_SEAL_GROW | \ > > - F_SEAL_WRITE) > > + F_SEAL_WRITE | \ > > + F_SEAL_FUTURE_WRITE) > > > > static int memfd_add_seals(struct file *file, unsigned int seals) > > { > > --- a/fs/hugetlbfs/inode.c~mm-add-an-f_seal_future_write-seal-to-memfd > > +++ a/fs/hugetlbfs/inode.c > > @@ -530,7 +530,7 @@ static long hugetlbfs_punch_hole(struct > > inode_lock(inode); > > > > /* protected by i_mutex */ > > - if (info->seals & F_SEAL_WRITE) { > > + if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) { > > inode_unlock(inode); > > return -EPERM; > > } > > --- a/mm/shmem.c~mm-add-an-f_seal_future_write-seal-to-memfd > > +++ a/mm/shmem.c > > @@ -2119,6 +2119,23 @@ out_nomem: > > > > static int shmem_mmap(struct file *file, struct vm_area_struct *vma) > > { > > + struct shmem_inode_info *info = SHMEM_I(file_inode(file)); > > + > > + /* > > + * New PROT_READ and MAP_SHARED mmaps are not allowed when "future > > PROT_WRITE, perhaps? Yes, fixed. > > + * write" seal active. > > + */ > > + if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE) && > > + (info->seals & F_SEAL_FUTURE_WRITE)) > > + return -EPERM; > > + > > + /* > > + * Since the F_SEAL_FUTURE_WRITE seals allow for a MAP_SHARED read-only > > + * mapping, take care to not allow mprotect to revert protections. > > + */ > > + if (info->seals & F_SEAL_FUTURE_WRITE) > > + vma->vm_flags &= ~(VM_MAYWRITE); > > + > > This might all be clearer as: > > if (info->seals & F_SEAL_FUTURE_WRITE) { > if (vma->vm_flags ...) > return -EPERM; > vma->vm_flags &= ~VM_MAYWRITE; > } > > with appropriate comments inserted. Agreed, its simpler. Updated patch is below. I squashed it with all the earlier ones. Andy, could you provide Acks and/or Reviewed-by tag as well? ---8<----------------------- >From b5a4960e755af67e9f6f9e65db5113e712cf338e Mon Sep 17 00:00:00 2001 From: "Joel Fernandes (Google)" Date: Sat, 10 Nov 2018 22:21:31 -0800 Subject: [PATCH v4] mm/memfd: Add an F_SEAL_FUTURE_WRITE seal to memfd Android uses ashmem for sharing memory regions. We are looking forward to migrating all usecases of ashmem to memfd so that we can possibly remove the ashmem driver in the future from staging while also benefiting from using memfd and contributing to it. Note staging drivers are also not ABI and generally can be removed at anytime. One of the main usecases Android has is the ability to create a region and mmap it as writeable, then add protection against making any "future" writes while keeping the existing already mmap'ed writeable-region active. This allows us to implement a usecase where receivers of the shared memory buffer can get a read-only view, while the sender continues to write to the buffer. See CursorWindow documentation in Android for more details: https://developer.android.com/reference/android/database/CursorWindow This usecase cannot be implemented with the existing F_SEAL_WRITE seal. To support the usecase, this patch adds a new F_SEAL_FUTURE_WRITE seal which prevents any future mmap and write syscalls from succeeding while keeping the existing mmap active. A better way to do F_SEAL_FUTURE_WRITE seal was discussed [1] last week where we don't need to modify core VFS structures to get the same behavior of the seal. This solves several side-effects pointed by Andy. self-tests are provided in later patch to verify the expected semantics. [1] https://lore.kernel.org/lkml/20181111173650.GA256781@google.com/ Suggested-by: Andy Lutomirski Signed-off-by: Joel Fernandes (Google) --- fs/hugetlbfs/inode.c | 2 +- include/uapi/linux/fcntl.h | 1 + mm/memfd.c | 3 ++- mm/shmem.c | 26 +++++++++++++++++++++++--- 4 files changed, 27 insertions(+), 5 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 762028994f47..5b54bf893a67 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -558,7 +558,7 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len) inode_lock(inode); /* protected by i_mutex */ - if (info->seals & F_SEAL_WRITE) { + if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) { inode_unlock(inode); return -EPERM; } diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 594b85f7cb86..1d338357df8a 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -41,6 +41,7 @@ #define F_SEAL_SHRINK 0x0002 /* prevent file from shrinking */ #define F_SEAL_GROW 0x0004 /* prevent file from growing */ #define F_SEAL_WRITE 0x0008 /* prevent writes */ +#define F_SEAL_FUTURE_WRITE 0x0010 /* prevent future writes while mapped */ /* (1U << 31) is reserved for signed error codes */ /* diff --git a/mm/memfd.c b/mm/memfd.c index 97264c79d2cd..650e65a46b9c 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -131,7 +131,8 @@ static unsigned int *memfd_file_seals_ptr(struct file *file) #define F_ALL_SEALS (F_SEAL_SEAL | \ F_SEAL_SHRINK | \ F_SEAL_GROW | \ - F_SEAL_WRITE) + F_SEAL_WRITE | \ + F_SEAL_FUTURE_WRITE) static int memfd_add_seals(struct file *file, unsigned int seals) { diff --git a/mm/shmem.c b/mm/shmem.c index 32eb29bd72c6..f5069e8225cc 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2121,6 +2121,25 @@ int shmem_lock(struct file *file, int lock, struct user_struct *user) static int shmem_mmap(struct file *file, struct vm_area_struct *vma) { + struct shmem_inode_info *info = SHMEM_I(file_inode(file)); + + + if (info->seals & F_SEAL_FUTURE_WRITE) { + /* + * New PROT_WRITE and MAP_SHARED mmaps are not allowed when + * "future write" seal active. + */ + if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE)) + return -EPERM; + + /* + * Since the F_SEAL_FUTURE_WRITE seals allow for a MAP_SHARED + * read-only mapping, take care to not allow mprotect to revert + * protections. + */ + vma->vm_flags &= ~(VM_MAYWRITE); + } + file_accessed(file); vma->vm_ops = &shmem_vm_ops; if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && @@ -2346,8 +2365,9 @@ shmem_write_begin(struct file *file, struct address_space *mapping, pgoff_t index = pos >> PAGE_SHIFT; /* i_mutex is held by caller */ - if (unlikely(info->seals & (F_SEAL_WRITE | F_SEAL_GROW))) { - if (info->seals & F_SEAL_WRITE) + if (unlikely(info->seals & (F_SEAL_GROW | + F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) { + if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) return -EPERM; if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size) return -EPERM; @@ -2610,7 +2630,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq); /* protected by i_mutex */ - if (info->seals & F_SEAL_WRITE) { + if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) { error = -EPERM; goto out; } -- 2.19.1.1215.g8438c0b245-goog