From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork.patch added to -mm tree Date: Sun, 09 Feb 2020 16:55:31 -0800 Message-ID: <20200210005531.c4Hj2dl6a%akpm@linux-foundation.org> References: <20200203173311.6269a8be06a05e5a4aa08a93@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:58064 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725868AbgBJAze (ORCPT ); Sun, 9 Feb 2020 19:55:34 -0500 In-Reply-To: <20200203173311.6269a8be06a05e5a4aa08a93@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: hannes@cmpxchg.org, kirill.shutemov@linux.intel.com, lixinhai.lxh@gmail.com, mm-commits@vger.kernel.org, riel@redhat.com, willy@infradead.org The patch titled Subject: mm: don't prepare anon_vma if vma has VM_WIPEONFORK has been added to the -mm tree. Its filename is mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Li Xinhai Subject: mm: don't prepare anon_vma if vma has VM_WIPEONFORK Patch series "mm: Fix misuse of parent anon_vma in dup_mmap path". This patchset fixes the misuse of parenet anon_vma, which mainly caused by child vma's vm_next and vm_prev are left same as its parent after duplicate vma. Finally, code reached parent vma's neighbor by referring pointer of child vma and executed wrong logic. The first two patches fix relevant issues, and the third patch sets vm_next and vm_prev to NULL when duplicate vma to prevent potential misuse in future. This patch (of 3): In dup_mmap(), anon_vma_prepare() is called for vma has VM_WIPEONFORK, and parameter 'tmp' (i.e., the new vma of child) has same ->vm_next and ->vm_prev as its parent vma. That allows anon_vma used by parent been mistakenly shared by child (find_mergeable_anon_vma() will do this reuse work). Besides this issue, call anon_vma_prepare() should be avoided because we don't copy page for this vma. Preparing anon_vma will be handled during fault. Link: http://lkml.kernel.org/r/1581150928-3214-2-git-send-email-lixinhai.lxh@gmail.com Fixes: d2cd9ede6e19 ("mm,fork: introduce MADV_WIPEONFORK") Signed-off-by: Li Xinhai Cc: Rik van Riel Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Johannes Weiner Signed-off-by: Andrew Morton --- kernel/fork.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/kernel/fork.c~mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork +++ a/kernel/fork.c @@ -552,10 +552,12 @@ static __latent_entropy int dup_mmap(str if (retval) goto fail_nomem_anon_vma_fork; if (tmp->vm_flags & VM_WIPEONFORK) { - /* VM_WIPEONFORK gets a clean slate in the child. */ + /* + * VM_WIPEONFORK gets a clean slate in the child. + * Don't prepare anon_vma until fault since we don't + * copy page for current vma. + */ tmp->anon_vma = NULL; - if (anon_vma_prepare(tmp)) - goto fail_nomem_anon_vma_fork; } else if (anon_vma_fork(tmp, mpnt)) goto fail_nomem_anon_vma_fork; tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT); _ Patches currently in -mm which might be from lixinhai.lxh@gmail.com are mm-dont-prepare-anon_vma-if-vma-has-vm_wipeonfork.patch revert-mm-rmapc-reuse-mergeable-anon_vma-as-parent-when-fork.patch mm-set-vm_next-and-vm_prev-to-null-in-vm_area_dup.patch