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=-6.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_GIT 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 D141BC468BD for ; Fri, 7 Jun 2019 15:43:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA5ED2146E for ; Fri, 7 Jun 2019 15:43:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559922191; bh=ihWvF9ruba1hnYDVsjmjftpcIcaGfogWK5Jvvp4ATI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=M3+JaZD/UPYKacigDLPCQTWneABe18o4xIF09z+5+BYpQ2+b53Uqlw+bCnTsMOmIJ utlk4syq/H5fX3SIW9GTQWcTYn5YQ1Vd3r65onTe7THA3ObWprbiqHKYRs+GhA9KVj n5peDTBqVOof9G6VnWU752tzXQssqOQPOrB4KMUo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730769AbfFGPnK (ORCPT ); Fri, 7 Jun 2019 11:43:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:54208 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730784AbfFGPnK (ORCPT ); Fri, 7 Jun 2019 11:43:10 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E2E2221479; Fri, 7 Jun 2019 15:43:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559922189; bh=ihWvF9ruba1hnYDVsjmjftpcIcaGfogWK5Jvvp4ATI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ysno1vbX22c9k4NCVY6wjIEXzBi9Jipoa4a+SFkLvv9tBSvNf7wIwlnqQ4neS0Ii0 RUBelejSwCnOsMHVxjK2iV/EmaXYhZ2QEnN6xU45wsJec9KCCTxfamC21qbMuZf5dG +W35aiJbej54KtKavJXDrwhfH+I76BIiB7I1Buow= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "ben.hutchings@codethink.co.uk, Alexander.Levin@microsoft.com, Joel Fernandes" , Ben Hutchings , Todd Kjos , Joel Fernandes Subject: [PATCH 4.14 68/69] binder: fix race between munmap() and direct reclaim Date: Fri, 7 Jun 2019 17:39:49 +0200 Message-Id: <20190607153856.182759891@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190607153848.271562617@linuxfoundation.org> References: <20190607153848.271562617@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Todd Kjos commit 5cec2d2e5839f9c0fec319c523a911e0a7fd299f upstream. An munmap() on a binder device causes binder_vma_close() to be called which clears the alloc->vma pointer. If direct reclaim causes binder_alloc_free_page() to be called, there is a race where alloc->vma is read into a local vma pointer and then used later after the mm->mmap_sem is acquired. This can result in calling zap_page_range() with an invalid vma which manifests as a use-after-free in zap_page_range(). The fix is to check alloc->vma after acquiring the mmap_sem (which we were acquiring anyway) and skip zap_page_range() if it has changed to NULL. Cc: Ben Hutchings Signed-off-by: Todd Kjos Reviewed-by: Joel Fernandes (Google) Cc: stable # 4.14 Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -945,14 +945,13 @@ enum lru_status binder_alloc_free_page(s index = page - alloc->pages; page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; + + mm = alloc->vma_vm_mm; + if (!mmget_not_zero(mm)) + goto err_mmget; + if (!down_write_trylock(&mm->mmap_sem)) + goto err_down_write_mmap_sem_failed; vma = binder_alloc_get_vma(alloc); - if (vma) { - if (!mmget_not_zero(alloc->vma_vm_mm)) - goto err_mmget; - mm = alloc->vma_vm_mm; - if (!down_write_trylock(&mm->mmap_sem)) - goto err_down_write_mmap_sem_failed; - } list_lru_isolate(lru, item); spin_unlock(lock); @@ -965,10 +964,9 @@ enum lru_status binder_alloc_free_page(s PAGE_SIZE); trace_binder_unmap_user_end(alloc, index); - - up_write(&mm->mmap_sem); - mmput(mm); } + up_write(&mm->mmap_sem); + mmput(mm); trace_binder_unmap_kernel_start(alloc, index);