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 1F30DC6FA8E for ; Sun, 26 Feb 2023 14:58:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231566AbjBZO6n (ORCPT ); Sun, 26 Feb 2023 09:58:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231153AbjBZO4G (ORCPT ); Sun, 26 Feb 2023 09:56:06 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BBA661CAF1; Sun, 26 Feb 2023 06:51:58 -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 25164B80C70; Sun, 26 Feb 2023 14:51:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2612FC433D2; Sun, 26 Feb 2023 14:51:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677423094; bh=++Gs8P30LiSIt+LSli+YK+qQUnGj5eH5qxStCqmYvWc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JA/JXWW6lW8Nw8LRPOPYzXLtAoBV7g5hKtN0QjO0wNOEpNfTSuNBMjnvRY7amLHRI pbwdKuBZtdiExdyFqbt6WqXt/uw6MPjPj9WTxQFEYKAobFn2UeTievTY7FzjLnnlfO F5uLU9NPdz3jt1wEdhbQOQU/f62Ma2QR6puxsldwm9GnGETu0m/k+aM4X2fCR6GAri FkfWfHwJ9qzfrmRYKC864fKGMOoi2BHfENS5Rla38SzzT0tmF5Oef1FdIZTXXMee9V uqoR3+rLKtr2919jfRqjwRl17dqQwjy8doWOCnuVmGC1DerlfEiDo9NoQ763vW7QQn tdE/k7ctllizg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Jann Horn , Thomas Gleixner , Sasha Levin , jirislaby@kernel.org Subject: [PATCH AUTOSEL 5.4 04/19] timers: Prevent union confusion from unexpected restart_syscall() Date: Sun, 26 Feb 2023 09:51:06 -0500 Message-Id: <20230226145123.829229-4-sashal@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230226145123.829229-1-sashal@kernel.org> References: <20230226145123.829229-1-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: Jann Horn [ Upstream commit 9f76d59173d9d146e96c66886b671c1915a5c5e5 ] The nanosleep syscalls use the restart_block mechanism, with a quirk: The `type` and `rmtp`/`compat_rmtp` fields are set up unconditionally on syscall entry, while the rest of the restart_block is only set up in the unlikely case that the syscall is actually interrupted by a signal (or pseudo-signal) that doesn't have a signal handler. If the restart_block was set up by a previous syscall (futex(..., FUTEX_WAIT, ...) or poll()) and hasn't been invalidated somehow since then, this will clobber some of the union fields used by futex_wait_restart() and do_restart_poll(). If userspace afterwards wrongly calls the restart_syscall syscall, futex_wait_restart()/do_restart_poll() will read struct fields that have been clobbered. This doesn't actually lead to anything particularly interesting because none of the union fields contain trusted kernel data, and futex(..., FUTEX_WAIT, ...) and poll() aren't syscalls where it makes much sense to apply seccomp filters to their arguments. So the current consequences are just of the "if userspace does bad stuff, it can damage itself, and that's not a problem" flavor. But still, it seems like a hazard for future developers, so invalidate the restart_block when partly setting it up in the nanosleep syscalls. Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230105134403.754986-1-jannh@google.com Signed-off-by: Sasha Levin --- kernel/time/hrtimer.c | 2 ++ kernel/time/posix-stubs.c | 2 ++ kernel/time/posix-timers.c | 2 ++ 3 files changed, 6 insertions(+) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index e1e8d5dab0c59..8e3c9228aec97 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -2020,6 +2020,7 @@ SYSCALL_DEFINE2(nanosleep, struct __kernel_timespec __user *, rqtp, if (!timespec64_valid(&tu)) return -EINVAL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE; current->restart_block.nanosleep.rmtp = rmtp; return hrtimer_nanosleep(&tu, HRTIMER_MODE_REL, CLOCK_MONOTONIC); @@ -2040,6 +2041,7 @@ SYSCALL_DEFINE2(nanosleep_time32, struct old_timespec32 __user *, rqtp, if (!timespec64_valid(&tu)) return -EINVAL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE; current->restart_block.nanosleep.compat_rmtp = rmtp; return hrtimer_nanosleep(&tu, HRTIMER_MODE_REL, CLOCK_MONOTONIC); diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c index 67df65f887ac8..8ddb35d9779cb 100644 --- a/kernel/time/posix-stubs.c +++ b/kernel/time/posix-stubs.c @@ -142,6 +142,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags, return -EINVAL; if (flags & TIMER_ABSTIME) rmtp = NULL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE; current->restart_block.nanosleep.rmtp = rmtp; return hrtimer_nanosleep(&t, flags & TIMER_ABSTIME ? @@ -228,6 +229,7 @@ SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags, return -EINVAL; if (flags & TIMER_ABSTIME) rmtp = NULL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE; current->restart_block.nanosleep.compat_rmtp = rmtp; return hrtimer_nanosleep(&t, flags & TIMER_ABSTIME ? diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 97d4a9dcf3399..efe3873021a37 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -1224,6 +1224,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags, return -EINVAL; if (flags & TIMER_ABSTIME) rmtp = NULL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_NATIVE : TT_NONE; current->restart_block.nanosleep.rmtp = rmtp; @@ -1251,6 +1252,7 @@ SYSCALL_DEFINE4(clock_nanosleep_time32, clockid_t, which_clock, int, flags, return -EINVAL; if (flags & TIMER_ABSTIME) rmtp = NULL; + current->restart_block.fn = do_no_restart_syscall; current->restart_block.nanosleep.type = rmtp ? TT_COMPAT : TT_NONE; current->restart_block.nanosleep.compat_rmtp = rmtp; -- 2.39.0