From patchwork Thu Oct 17 15:10:07 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thomas Hellstrom X-Patchwork-Id: 13840191 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 47F64D374A4 for ; Thu, 17 Oct 2024 15:10:29 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B443810E861; Thu, 17 Oct 2024 15:10:28 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="btN0CXLs"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id AB5D710E85A; Thu, 17 Oct 2024 15:10:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1729177826; x=1760713826; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=6XP/LzTB3nvKYFWkVuM1f8jskS31WWEbgTeV8UCE0d8=; b=btN0CXLs4Z1lAqptz3w4tTk6D5lPC6XheemZUIbHhyxcsIGve9IRtCB9 32cKmKYFUZ3y1XPecrnmSbuuHDK9lnxX0vtc8HGR8efPSXYc1R4C5CNni 29/uuTQ33oRs6acovgzPRLn3nQUbPK1prYCi9DJ6lBeZjEvFkKxHLrhaN 9ro7S38gjTcvBgra5bFYfAGR0teXEqgTYgtMgZ4ortlJumDNG7iZrV5uW k1H39DTtAIz9wpULEQrO9i+YgzJ7BJKFMAFDHLiqOs5KofEo0MRkDqTrn 5kqefjRtmDy8jCPIqimtuZNvn7nAbV99oxy8TvaXJMvj8AwPbrzi7OCHB g==; X-CSE-ConnectionGUID: faMBtudFRFK6zT93e8X4/g== X-CSE-MsgGUID: 31UqqXWtQvK+iD5H/6KyGg== X-IronPort-AV: E=McAfee;i="6700,10204,11222"; a="32351257" X-IronPort-AV: E=Sophos;i="6.11,199,1725346800"; d="scan'208";a="32351257" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2024 08:10:26 -0700 X-CSE-ConnectionGUID: VZBLmX2CTKqnKAJCN9HErw== X-CSE-MsgGUID: BxKVCxrIRHe9gJtNIRMSzQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,211,1725346800"; d="scan'208";a="101885038" Received: from cpetruta-mobl1.ger.corp.intel.com (HELO fedora..) ([10.245.246.150]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2024 08:10:22 -0700 From: =?utf-8?q?Thomas_Hellstr=C3=B6m?= To: intel-xe@lists.freedesktop.org Cc: =?utf-8?q?Thomas_Hellstr=C3=B6m?= , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Maarten Lankhorst , =?utf-8?q?Christian_K=C3=B6nig?= , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, maarten.lankhorst@linux.intel.com Subject: [PATCH v3] locking/ww_mutex: Adjust to lockdep nest_lock requirements Date: Thu, 17 Oct 2024 17:10:07 +0200 Message-ID: <20241017151007.92215-1-thomas.hellstrom@linux.intel.com> X-Mailer: git-send-email 2.46.0 MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" When using mutex_acquire_nest() with a nest_lock, lockdep refcounts the number of acquired lockdep_maps of mutexes of the same class, and also keeps a pointer to the first acquired lockdep_map of a class. That pointer is then used for various comparison-, printing- and checking purposes, but there is no mechanism to actively ensure that lockdep_map stays in memory. Instead, a warning is printed if the lockdep_map is freed and there are still held locks of the same lock class, even if the lockdep_map itself has been released. In the context of WW/WD transactions that means that if a user unlocks and frees a ww_mutex from within an ongoing ww transaction, and that mutex happens to be the first ww_mutex grabbed in the transaction, such a warning is printed and there might be a risk of a UAF. Note that this is only problem when lockdep is enabled and affects only dereferences of struct lockdep_map. Adjust to this by adding a fake lockdep_map to the acquired context and make sure it is the first acquired lockdep map of the associated ww_mutex class. Then hold it for the duration of the WW/WD transaction. This has the side effect that trying to lock a ww mutex *without* a ww_acquire_context but where a such context has been acquire, we'd see a lockdep splat. The test-ww_mutex.c selftest attempts to do that, so modify that particular test to not acquire a ww_acquire_context if it is not going to be used. v2: - Lower the number of locks in the test-ww_mutex stress(STRESS_ALL) test to accommodate the dummy lock introduced in this patch without overflowing lockdep held lock references. v3: - Adjust the ww_test_normal locking-api selftest to avoid recursive locking (Boqun Feng) - Initialize the dummy lock map with LD_WAIT_SLEEP to agree with how the corresponding ww_mutex lockmaps are initialized (Boqun Feng) Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: Maarten Lankhorst Cc: Christian König Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Thomas Hellström Acked-by: maarten.lankhorst@linux.intel.com #v1 Signed-off-by: Boqun Feng Tested-by: Boqun Feng --- include/linux/ww_mutex.h | 14 ++++++++++++++ kernel/locking/test-ww_mutex.c | 8 +++++--- lib/locking-selftest.c | 4 ++-- 3 files changed, 21 insertions(+), 5 deletions(-) diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index bb763085479a..45ff6f7a872b 100644 --- a/include/linux/ww_mutex.h +++ b/include/linux/ww_mutex.h @@ -65,6 +65,16 @@ struct ww_acquire_ctx { #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; + /** + * @first_lock_dep_map: fake lockdep_map for first locked ww_mutex. + * + * lockdep requires the lockdep_map for the first locked ww_mutex + * in a ww transaction to remain in memory until all ww_mutexes of + * the transaction have been unlocked. Ensure this by keeping a + * fake locked ww_mutex lockdep map between ww_acquire_init() and + * ww_acquire_fini(). + */ + struct lockdep_map first_lock_dep_map; #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH unsigned int deadlock_inject_interval; @@ -146,7 +156,10 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, &ww_class->acquire_key, 0); + lockdep_init_map_wait(&ctx->first_lock_dep_map, ww_class->mutex_name, + &ww_class->mutex_key, 0, LD_WAIT_SLEEP); mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); + mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx->dep_map, _RET_IP_); #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH ctx->deadlock_inject_interval = 1; @@ -185,6 +198,7 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) { #ifdef CONFIG_DEBUG_LOCK_ALLOC + mutex_release(&ctx->first_lock_dep_map, _THIS_IP_); mutex_release(&ctx->dep_map, _THIS_IP_); #endif #ifdef DEBUG_WW_MUTEXES diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 10a5736a21c2..5d58b2c0ef98 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -62,7 +62,8 @@ static int __test_mutex(unsigned int flags) int ret; ww_mutex_init(&mtx.mutex, &ww_class); - ww_acquire_init(&ctx, &ww_class); + if (flags & TEST_MTX_CTX) + ww_acquire_init(&ctx, &ww_class); INIT_WORK_ONSTACK(&mtx.work, test_mutex_work); init_completion(&mtx.ready); @@ -90,7 +91,8 @@ static int __test_mutex(unsigned int flags) ret = wait_for_completion_timeout(&mtx.done, TIMEOUT); } ww_mutex_unlock(&mtx.mutex); - ww_acquire_fini(&ctx); + if (flags & TEST_MTX_CTX) + ww_acquire_fini(&ctx); if (ret) { pr_err("%s(flags=%x): mutual exclusion failure\n", @@ -679,7 +681,7 @@ static int __init test_ww_mutex_init(void) if (ret) return ret; - ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); + ret = stress(2046, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); if (ret) return ret; diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 6f6a5fc85b42..6750321e3e9a 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -1720,8 +1720,6 @@ static void ww_test_normal(void) { int ret; - WWAI(&t); - /* * None of the ww_mutex codepaths should be taken in the 'normal' * mutex calls. The easiest way to verify this is by using the @@ -1770,6 +1768,8 @@ static void ww_test_normal(void) ww_mutex_base_unlock(&o.base); WARN_ON(o.ctx != (void *)~0UL); + WWAI(&t); + /* nest_lock */ o.ctx = (void *)~0UL; ww_mutex_base_lock_nest_lock(&o.base, &t);