From patchwork Wed Oct 9 09:20:31 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thomas Hellstrom X-Patchwork-Id: 13827985 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 47F63CED63F for ; Wed, 9 Oct 2024 09:20:51 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C238010E6B1; Wed, 9 Oct 2024 09:20:50 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="FJlB3ykK"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) by gabe.freedesktop.org (Postfix) with ESMTPS id DDE2F10E6AA; Wed, 9 Oct 2024 09:20:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1728465649; x=1760001649; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=Pd3SHnCEE8moULvhFWXTFLWNeS6Qs4kOTEaFTwtkVqQ=; b=FJlB3ykKcIVQ+n7vQpUPvCmI1LMydh6OXkkuSAlS/ZD38CW651EhgczD fDRMTlRfxVpz78tGSAF63bM09pWhfPJrZqNc3oCA1PcpnZd7AKNA/dV1Z QuebQ4H4YfpENxpqsWYplcdIG70GoiX/PiU1Sllp+KUo3psVXk3oeqhns 2MO1ouQRK4mlXJYf0N8wkNfETEG0/IKh4Qy8Or+dJ4v2E0lZ3G7zSwKaf VbjvgY5MEUgxqu7jBHmFcf6ueFt5sTBGr23SbL83xqv3gpbH8cvqEyYxj 9H87qn/bnHoMCjeusIwnKDWxxtIH2iQCYnf96RKnRTqCysXwZBeqq7ocN A==; X-CSE-ConnectionGUID: UcbWQY/PRwSKkWzmVivDAg== X-CSE-MsgGUID: WWj7QeuYSiST1UYDA9xsIQ== X-IronPort-AV: E=McAfee;i="6700,10204,11219"; a="27911558" X-IronPort-AV: E=Sophos;i="6.11,189,1725346800"; d="scan'208";a="27911558" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2024 02:20:43 -0700 X-CSE-ConnectionGUID: M3tE0CP0Rbm7CoBNBsufWg== X-CSE-MsgGUID: qnSrorKTRh+L3b2pZjyoOA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,189,1725346800"; d="scan'208";a="76625385" Received: from oandoniu-mobl3.ger.corp.intel.com (HELO fedora..) ([10.245.245.243]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2024 02:20:40 -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 Subject: [PATCH v2] locking/ww_mutex: Adjust to lockdep nest_lock requirements Date: Wed, 9 Oct 2024 11:20:31 +0200 Message-ID: <20241009092031.6356-1-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. 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 --- include/linux/ww_mutex.h | 14 ++++++++++++++ kernel/locking/test-ww_mutex.c | 8 +++++--- 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index bb763085479a..a401a2f31a77 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(&ctx->first_lock_dep_map, ww_class->mutex_name, + &ww_class->mutex_key, 0); 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;