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 71072C433FE for ; Mon, 28 Nov 2022 09:51:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230046AbiK1JvN (ORCPT ); Mon, 28 Nov 2022 04:51:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230035AbiK1JvE (ORCPT ); Mon, 28 Nov 2022 04:51:04 -0500 Received: from mail-wm1-x349.google.com (mail-wm1-x349.google.com [IPv6:2a00:1450:4864:20::349]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 657FE193C3 for ; Mon, 28 Nov 2022 01:51:02 -0800 (PST) Received: by mail-wm1-x349.google.com with SMTP id b47-20020a05600c4aaf00b003d031aeb1b6so8335761wmp.9 for ; Mon, 28 Nov 2022 01:51:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Cct04cXs5K6Oma9vXfMm60p6i+CfzdxpxLX+V58OiqQ=; b=F8rWO4eEUv81PuSKtmYCtH6WPMr3pJLLQVDBUG+mf3OIy/GgnIfAfRBTjQOuF0NZgI rQCvXESuwjsM+T6ALxE15HiEcWvtzdF69PXuMMgl9Gp8SOqnwRANXg4WM8IESG8AGx+s edceQgh2LwiydLOf165rabsPFjFB86SOAH4c/BT53evJVpZn4lRm6K5ImDhjrnhFx4Of XIQSsEb6/zUJG5A4gX+KMJ0FUtrijmXIqWZFaH/WZmcDXYjJU491FhbK5snqi54h7p/V 37ylxNxeU1MNJLXAM5OGWTPcUV0xqWEL7LQAoqOZ4ol27gM4g+vEdJinXsOfbPbuXFPD MJEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Cct04cXs5K6Oma9vXfMm60p6i+CfzdxpxLX+V58OiqQ=; b=mGDmE/ZIzLmbxq/WzHItTaSBBn/U36ekDff7uWyEG96Nr1ha1AUzmy/p46yiVpxkic RtQDGqm3qYefO617r9Ge+TP6ltc2+Be81Kp2UINc3esTLFnisFfEUfLgla9YNGUqX4bE JUzuua/De4CoKe2wUct8riYzNm8nLNknxDlQYC5Eh5FDvxQEjGecU/hI2xKX7lJJn2I7 0CfIPDTpHWP0YKzKnof1W1uBIu9uF4peJc4Op+HLvN8hYBzvQoLT4zLDOxdtKKoHpAv2 YTAH7LQ1Wo78+RVQpOB1KIWXv4tAzpm9d5RNfyYVfGCQqyxpcKZ6IJju3m1fXiGtLIDz 8frA== X-Gm-Message-State: ANoB5plbZ0qfPQIbqS/xP4QsUvvm0+Fjd7aQYwZcJJO5LjwBFBqh9zPJ E4zLgbCUtq8fTimailr0RxkAJv+6b2M= X-Google-Smtp-Source: AA0mqf47reGLvqtfhUicf3SwZLCRiQSU8ElrY3uGc5tGFXHC/qU5NVNZWlAkGfegPCyHFwdpnlPxg1K7kmE= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:dc07:26e3:1eb7:b279]) (user=glider job=sendgmr) by 2002:a5d:6dcf:0:b0:236:78b7:87c9 with SMTP id d15-20020a5d6dcf000000b0023678b787c9mr30120679wrz.556.1669629060947; Mon, 28 Nov 2022 01:51:00 -0800 (PST) Date: Mon, 28 Nov 2022 10:45:41 +0100 In-Reply-To: <20221128094541.2645890-1-glider@google.com> Mime-Version: 1.0 References: <20221128094541.2645890-1-glider@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog Message-ID: <20221128094541.2645890-2-glider@google.com> Subject: [PATCH 2/2] kmsan: allow using __msan_instrument_asm_store() inside runtime From: Alexander Potapenko To: glider@google.com Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, elver@google.com, dvyukov@google.com, linux-mm@kvack.org, kasan-dev@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In certain cases (e.g. when handling a softirq) __msan_instrument_asm_store(&var, sizeof(var)) may be called with from within KMSAN runtime, but later the value of @var is used with !kmsan_in_runtime(), leading to false positives. Because kmsan_internal_unpoison_memory() doesn't take locks, it should be fine to call it without kmsan_in_runtime() checks, which fixes the mentioned false positives. Signed-off-by: Alexander Potapenko --- mm/kmsan/instrumentation.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/kmsan/instrumentation.c b/mm/kmsan/instrumentation.c index 271f135f97a16..770fe02904f36 100644 --- a/mm/kmsan/instrumentation.c +++ b/mm/kmsan/instrumentation.c @@ -81,12 +81,16 @@ DECLARE_METADATA_PTR_GETTER(8); * Handle a memory store performed by inline assembly. KMSAN conservatively * attempts to unpoison the outputs of asm() directives to prevent false * positives caused by missed stores. + * + * __msan_instrument_asm_store() may be called for inline assembly code when + * entering or leaving IRQ. We omit the check for kmsan_in_runtime() to ensure + * the memory written to in these cases is also marked as initialized. */ void __msan_instrument_asm_store(void *addr, uintptr_t size) { unsigned long ua_flags; - if (!kmsan_enabled || kmsan_in_runtime()) + if (!kmsan_enabled) return; ua_flags = user_access_save(); @@ -103,10 +107,8 @@ void __msan_instrument_asm_store(void *addr, uintptr_t size) user_access_restore(ua_flags); return; } - kmsan_enter_runtime(); /* Unpoisoning the memory on best effort. */ kmsan_internal_unpoison_memory(addr, size, /*checked*/ false); - kmsan_leave_runtime(); user_access_restore(ua_flags); } EXPORT_SYMBOL(__msan_instrument_asm_store); -- 2.38.1.584.g0f3c55d4c2-goog