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 87AD0C7EE23 for ; Sun, 26 Feb 2023 14:56:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231416AbjBZO4N (ORCPT ); Sun, 26 Feb 2023 09:56:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231201AbjBZOzG (ORCPT ); Sun, 26 Feb 2023 09:55:06 -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 D12F313D58; Sun, 26 Feb 2023 06:50:46 -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 8662360C50; Sun, 26 Feb 2023 14:50:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46332C4339C; Sun, 26 Feb 2023 14:50:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677423035; bh=T8EyDmS3c8KWcIlZlLCyElCSMUibYnr7czwvsQskVAA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B1BaznLC3uy//XuedGqaHLwOKqg5txWwgQlq3RPpRdjcfrQQt7fPRDSuU5/cRDPgj CuGadKBoGD+JIML4ZruNrbhC6zN53VyySQQC3iH0XOhlPWPq7m42Q4D9xWHHetYlJD UftATxyMXiNh4kKgCvCH9vt7PZDzs05COkb51RLdMGDi7FQK0mrcA4NJjqGlHni0rp EfwYZykTBp3YFGnBwAv5TpH7BatEGJq/bsgplWRcWEY2pj/565GwRR12Nz5qJDNUde 6fE3UuCwmy/+/1A2kS225F/l+b8X9gT0GoDustIHFtGxDqj+us4zXvo0rha4gWSO74 saEB/oBv23CWw== 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 5.10 08/27] timers: Prevent union confusion from unexpected restart_syscall() Date: Sun, 26 Feb 2023 09:49:55 -0500 Message-Id: <20230226145014.828855-8-sashal@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230226145014.828855-1-sashal@kernel.org> References: <20230226145014.828855-1-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 544ce87ba38a7..70deb2f01e97a 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -2024,6 +2024,7 @@ 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(timespec64_to_ktime(tu), HRTIMER_MODE_REL, @@ -2045,6 +2046,7 @@ 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(timespec64_to_ktime(tu), HRTIMER_MODE_REL, diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c index fcb3b21d8bdcd..3783d07d60ba0 100644 --- a/kernel/time/posix-stubs.c +++ b/kernel/time/posix-stubs.c @@ -146,6 +146,7 @@ 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; texp = timespec64_to_ktime(t); @@ -239,6 +240,7 @@ 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; texp = timespec64_to_ktime(t); diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index b624788023d8f..724ca7eb1a6e8 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -1270,6 +1270,7 @@ 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; @@ -1297,6 +1298,7 @@ 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