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[209.132.180.67]) by mx.google.com with ESMTP id b22si2048394pjo.46.2019.06.07.08.46.17; Fri, 07 Jun 2019 08:46:34 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=Ysno1vbX; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730799AbfFGPnM (ORCPT + 99 others); Fri, 7 Jun 2019 11:43:12 -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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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);