From patchwork Mon Jan 24 18:42:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 534932 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 E7C1DC43217 for ; Tue, 25 Jan 2022 00:08:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2369526AbiAYACB (ORCPT ); Mon, 24 Jan 2022 19:02:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1383546AbiAXX2E (ORCPT ); Mon, 24 Jan 2022 18:28:04 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 078F0C01D7F4; Mon, 24 Jan 2022 13:31:32 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B7411B8123A; Mon, 24 Jan 2022 21:31:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D92EDC340E4; Mon, 24 Jan 2022 21:31:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643059889; bh=fgpNcpGwTQOlUCWiGZGZm/cuplCzU4SORglq/H8Knog=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DOEPQTnoQ4QCsWO3YTxIGx5181+xQOzM0bMSKw/6O6vlvShj6yg1haeA5P+HslsY1 3VGf7kYQYvH9RHCAJau7g5o+wmXPtJkGxO/NJLhuB9m4DvYgcCOPbRhn3ywkZF/VJY 5nb0q+xixIcuL4X9oB6iEJCm9tu6tDTktM3d6Hrw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michael Ellerman , Sasha Levin Subject: [PATCH 5.16 0769/1039] selftests/powerpc: Add a test of sigreturning to the kernel Date: Mon, 24 Jan 2022 19:42:38 +0100 Message-Id: <20220124184151.159121523@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184125.121143506@linuxfoundation.org> References: <20220124184125.121143506@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Michael Ellerman [ Upstream commit a8968521cfdc3e339fe69473d6632e0aa8d7202a ] We have a general signal fuzzer, sigfuz, which can modify the MSR & NIP before sigreturn. But the chance of it hitting a kernel address and also clearing MSR_PR is fairly slim. So add a specific test of sigreturn to a kernel address, both with and without attempting to clear MSR_PR (which the kernel must block). Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211209115944.4062384-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin --- .../selftests/powerpc/signal/.gitignore | 1 + .../testing/selftests/powerpc/signal/Makefile | 1 + .../powerpc/signal/sigreturn_kernel.c | 132 ++++++++++++++++++ 3 files changed, 134 insertions(+) create mode 100644 tools/testing/selftests/powerpc/signal/sigreturn_kernel.c diff --git a/tools/testing/selftests/powerpc/signal/.gitignore b/tools/testing/selftests/powerpc/signal/.gitignore index ce3375cd8e73e..8f6c816099a48 100644 --- a/tools/testing/selftests/powerpc/signal/.gitignore +++ b/tools/testing/selftests/powerpc/signal/.gitignore @@ -4,3 +4,4 @@ signal_tm sigfuz sigreturn_vdso sig_sc_double_restart +sigreturn_kernel diff --git a/tools/testing/selftests/powerpc/signal/Makefile b/tools/testing/selftests/powerpc/signal/Makefile index d6ae54663aed7..84e201572466d 100644 --- a/tools/testing/selftests/powerpc/signal/Makefile +++ b/tools/testing/selftests/powerpc/signal/Makefile @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 TEST_GEN_PROGS := signal signal_tm sigfuz sigreturn_vdso sig_sc_double_restart +TEST_GEN_PROGS += sigreturn_kernel CFLAGS += -maltivec $(OUTPUT)/signal_tm: CFLAGS += -mhtm diff --git a/tools/testing/selftests/powerpc/signal/sigreturn_kernel.c b/tools/testing/selftests/powerpc/signal/sigreturn_kernel.c new file mode 100644 index 0000000000000..0a1b6e591eeed --- /dev/null +++ b/tools/testing/selftests/powerpc/signal/sigreturn_kernel.c @@ -0,0 +1,132 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Test that we can't sigreturn to kernel addresses, or to kernel mode. + */ + +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include + +#include "utils.h" + +#define MSR_PR (1ul << 14) + +static volatile unsigned long long sigreturn_addr; +static volatile unsigned long long sigreturn_msr_mask; + +static void sigusr1_handler(int signo, siginfo_t *si, void *uc_ptr) +{ + ucontext_t *uc = (ucontext_t *)uc_ptr; + + if (sigreturn_addr) + UCONTEXT_NIA(uc) = sigreturn_addr; + + if (sigreturn_msr_mask) + UCONTEXT_MSR(uc) &= sigreturn_msr_mask; +} + +static pid_t fork_child(void) +{ + pid_t pid; + + pid = fork(); + if (pid == 0) { + raise(SIGUSR1); + exit(0); + } + + return pid; +} + +static int expect_segv(pid_t pid) +{ + int child_ret; + + waitpid(pid, &child_ret, 0); + FAIL_IF(WIFEXITED(child_ret)); + FAIL_IF(!WIFSIGNALED(child_ret)); + FAIL_IF(WTERMSIG(child_ret) != 11); + + return 0; +} + +int test_sigreturn_kernel(void) +{ + struct sigaction act; + int child_ret, i; + pid_t pid; + + act.sa_sigaction = sigusr1_handler; + act.sa_flags = SA_SIGINFO; + sigemptyset(&act.sa_mask); + + FAIL_IF(sigaction(SIGUSR1, &act, NULL)); + + for (i = 0; i < 2; i++) { + // Return to kernel + sigreturn_addr = 0xcull << 60; + pid = fork_child(); + expect_segv(pid); + + // Return to kernel virtual + sigreturn_addr = 0xc008ull << 48; + pid = fork_child(); + expect_segv(pid); + + // Return out of range + sigreturn_addr = 0xc010ull << 48; + pid = fork_child(); + expect_segv(pid); + + // Return to no-man's land, just below PAGE_OFFSET + sigreturn_addr = (0xcull << 60) - (64 * 1024); + pid = fork_child(); + expect_segv(pid); + + // Return to no-man's land, above TASK_SIZE_4PB + sigreturn_addr = 0x1ull << 52; + pid = fork_child(); + expect_segv(pid); + + // Return to 0xd space + sigreturn_addr = 0xdull << 60; + pid = fork_child(); + expect_segv(pid); + + // Return to 0xe space + sigreturn_addr = 0xeull << 60; + pid = fork_child(); + expect_segv(pid); + + // Return to 0xf space + sigreturn_addr = 0xfull << 60; + pid = fork_child(); + expect_segv(pid); + + // Attempt to set PR=0 for 2nd loop (should be blocked by kernel) + sigreturn_msr_mask = ~MSR_PR; + } + + printf("All children killed as expected\n"); + + // Don't change address, just MSR, should return to user as normal + sigreturn_addr = 0; + sigreturn_msr_mask = ~MSR_PR; + pid = fork_child(); + waitpid(pid, &child_ret, 0); + FAIL_IF(!WIFEXITED(child_ret)); + FAIL_IF(WIFSIGNALED(child_ret)); + FAIL_IF(WEXITSTATUS(child_ret) != 0); + + return 0; +} + +int main(void) +{ + return test_harness(test_sigreturn_kernel, "sigreturn_kernel"); +}