From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 75FF01E32C8; Sun, 24 Nov 2024 12:47:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732452430; cv=none; b=YGShr+W5ikFI6IXyAkcJE8fGa+iWLpHl9uWWml6dguT/anKG3JJIvnGS+C/fyTomzxS7cGm0r1cZGpG8bC/+Uv2nJwBfiqGlM31XdEQcNM64PtVJhBDMBOh1kzXiT3IEHVnoneP876tc66OEsSQ8xE56Gdork7Bu6EB7CZdtSag= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732452430; c=relaxed/simple; bh=MtiqgoI2o/vw98DXdP0vCH0oo6iL6enNCXHHH09oO28=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=sDrQBGMy88OwimsZxszW6COEBGmYOUW5KBqFZq8ST3sp/zjW7ouupg4csGKXw5yitGtTRGEXbBH5nKtSC2ImhTPrty0HCrXnHNcNsk62OsV86oF5FK8aAglB24qOrRCbLZlGa80hAvfSj/MHHGAncaYhOrvUWbsU89dUGp/HWKM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NgOs3g76; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NgOs3g76" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 887BFC4CECC; Sun, 24 Nov 2024 12:47:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732452430; bh=MtiqgoI2o/vw98DXdP0vCH0oo6iL6enNCXHHH09oO28=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NgOs3g76R4EboGitYPOkElS9jd/ZYsPfs0tljO3QLiHc07YURm0gzfULXj/SrfedZ JVHQV4uvhkRqO+MyZGzOtko2AbjAedMbdoRlEyZ4oaowBIelhgYOO773+lj3BhQJ6A 2nxKB0w6JCz/HXPoIaKLpUnzd8wmG5rDswEjiP893QEk2Vr3HMya/esR2nr40Ps4ep yg+6SxZlu15JdPiG7YJepaXXTDtyLSSf6KmFDaAhlM10aj/LIorpCGoRFOAvIb7FID 1XSqNMAE7kKLjpqWOjEsY8wdO2V3IVYvshRdo+IKnFSrakvlpyG/AV9GtkohFkL0te oMlLdnp1MPqkg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Peter Zijlstra , Sasha Levin , mingo@redhat.com, will@kernel.org Subject: [PATCH AUTOSEL 6.6 3/4] locking/ww_mutex: Adjust to lockdep nest_lock requirements Date: Sun, 24 Nov 2024 07:46:57 -0500 Message-ID: <20241124124702.3338309-3-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241124124702.3338309-1-sashal@kernel.org> References: <20241124124702.3338309-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.63 Content-Transfer-Encoding: 8bit From: Thomas Hellström [ Upstream commit 823a566221a5639f6c69424897218e5d6431a970 ] 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. Signed-off-by: Thomas Hellström Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241009092031.6356-1-thomas.hellstrom@linux.intel.com Signed-off-by: Sasha Levin --- 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 bb763085479af..a401a2f31a775 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 7c5a8f05497f2..02b84288865ca 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", @@ -663,7 +665,7 @@ 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; -- 2.43.0