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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6AE86C433EF for ; Tue, 15 Feb 2022 15:31:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240280AbiBOPcE (ORCPT ); Tue, 15 Feb 2022 10:32:04 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:49634 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240234AbiBOPap (ORCPT ); Tue, 15 Feb 2022 10:30:45 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5415C12D5; Tue, 15 Feb 2022 07:29:00 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 3ED2C615CE; Tue, 15 Feb 2022 15:29:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCE0CC36AE3; Tue, 15 Feb 2022 15:28:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644938939; bh=fPzhcJUNc782pRynNz+kxubVhm6EiTsyUtZufSvYyDg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Se4y0jkdVaqUfAvH9BvnBZUfweoVkZEpJk2Pxb8ln/uTTY+nrdRY4Niw3kaELo3hF Y98ZLKuhwnzTWou9PZXXz0Vd2dG0e5IBKOEXBEBmd3PkvNvd+m+LAy+ivYkaqYvfMv tLTc8YSPt+QfmiMPa1ITdoRRJNf61nKXcP0ezpcFTiWiC7AAvhM2dRvuPzjU9WPfnS sUuxhFof/1nkK6DcKSZ4EEIYlHCO/w0C+A/mwD63ZP4L+1wAL8Fxnz8JMC/2qtzEXp 6weLqma+FI5+feHfTODzUdRlpCRVBIY7Lf+ROcjiDtJfn3L6El8GFgRTAakP9MXU11 55olLhZ/bbhLQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Axel Rasmussen , Christian Brauner , Shuah Khan , Sasha Levin , shuah@kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 15/33] pidfd: fix test failure due to stack overflow on some arches Date: Tue, 15 Feb 2022 10:28:13 -0500 Message-Id: <20220215152831.580780-15-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220215152831.580780-1-sashal@kernel.org> References: <20220215152831.580780-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Axel Rasmussen [ Upstream commit 4cbd93c3c110447adc66cb67c08af21f939ae2d7 ] When running the pidfd_fdinfo_test on arm64, it fails for me. After some digging, the reason is that the child exits due to SIGBUS, because it overflows the 1024 byte stack we've reserved for it. To fix the issue, increase the stack size to 8192 bytes (this number is somewhat arbitrary, and was arrived at through experimentation -- I kept doubling until the failure no longer occurred). Also, let's make the issue easier to debug. wait_for_pid() returns an ambiguous value: it may return -1 in all of these cases: 1. waitpid() itself returned -1 2. waitpid() returned success, but we found !WIFEXITED(status). 3. The child process exited, but it did so with a -1 exit code. There's no way for the caller to tell the difference. So, at least log which occurred, so the test runner can debug things. While debugging this, I found that we had !WIFEXITED(), because the child exited due to a signal. This seems like a reasonably common case, so also print out whether or not we have WIFSIGNALED(), and the associated WTERMSIG() (if any). This lets us see the SIGBUS I'm fixing clearly when it occurs. Finally, I'm suspicious of allocating the child's stack on our stack. man clone(2) suggests that the correct way to do this is with mmap(), and in particular by setting MAP_STACK. So, switch to doing it that way instead. Signed-off-by: Axel Rasmussen Acked-by: Christian Brauner Signed-off-by: Shuah Khan Signed-off-by: Sasha Levin --- tools/testing/selftests/pidfd/pidfd.h | 13 ++++++++--- .../selftests/pidfd/pidfd_fdinfo_test.c | 22 +++++++++++++++---- 2 files changed, 28 insertions(+), 7 deletions(-) diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h index 01f8d3c0cf2cb..6922d6417e1cf 100644 --- a/tools/testing/selftests/pidfd/pidfd.h +++ b/tools/testing/selftests/pidfd/pidfd.h @@ -68,7 +68,7 @@ #define PIDFD_SKIP 3 #define PIDFD_XFAIL 4 -int wait_for_pid(pid_t pid) +static inline int wait_for_pid(pid_t pid) { int status, ret; @@ -78,13 +78,20 @@ int wait_for_pid(pid_t pid) if (errno == EINTR) goto again; + ksft_print_msg("waitpid returned -1, errno=%d\n", errno); return -1; } - if (!WIFEXITED(status)) + if (!WIFEXITED(status)) { + ksft_print_msg( + "waitpid !WIFEXITED, WIFSIGNALED=%d, WTERMSIG=%d\n", + WIFSIGNALED(status), WTERMSIG(status)); return -1; + } - return WEXITSTATUS(status); + ret = WEXITSTATUS(status); + ksft_print_msg("waitpid WEXITSTATUS=%d\n", ret); + return ret; } static inline int sys_pidfd_open(pid_t pid, unsigned int flags) diff --git a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c index 22558524f71c3..3fd8e903118f5 100644 --- a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c +++ b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c @@ -12,6 +12,7 @@ #include #include #include +#include #include "pidfd.h" #include "../kselftest.h" @@ -80,7 +81,10 @@ static inline int error_check(struct error *err, const char *test_name) return err->code; } +#define CHILD_STACK_SIZE 8192 + struct child { + char *stack; pid_t pid; int fd; }; @@ -89,17 +93,22 @@ static struct child clone_newns(int (*fn)(void *), void *args, struct error *err) { static int flags = CLONE_PIDFD | CLONE_NEWPID | CLONE_NEWNS | SIGCHLD; - size_t stack_size = 1024; - char *stack[1024] = { 0 }; struct child ret; if (!(flags & CLONE_NEWUSER) && geteuid() != 0) flags |= CLONE_NEWUSER; + ret.stack = mmap(NULL, CHILD_STACK_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0); + if (ret.stack == MAP_FAILED) { + error_set(err, -1, "mmap of stack failed (errno %d)", errno); + return ret; + } + #ifdef __ia64__ - ret.pid = __clone2(fn, stack, stack_size, flags, args, &ret.fd); + ret.pid = __clone2(fn, ret.stack, CHILD_STACK_SIZE, flags, args, &ret.fd); #else - ret.pid = clone(fn, stack + stack_size, flags, args, &ret.fd); + ret.pid = clone(fn, ret.stack + CHILD_STACK_SIZE, flags, args, &ret.fd); #endif if (ret.pid < 0) { @@ -129,6 +138,11 @@ static inline int child_join(struct child *child, struct error *err) else if (r > 0) error_set(err, r, "child %d reported: %d", child->pid, r); + if (munmap(child->stack, CHILD_STACK_SIZE)) { + error_set(err, -1, "munmap of child stack failed (errno %d)", errno); + r = -1; + } + return r; } -- 2.34.1