From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CCAABA927 for ; Thu, 3 Apr 2025 00:08:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743638921; cv=none; b=F6G8e7BiQnCdMHeEIs7JbzLpz1vuPje7u1Eotm6htddUQkkV1R765iI/fwd0+Mkv0cZV8OerJokvvXkrhdhUHMfIYXmbanwmqDkYyaOsJmuuojYvZk6hpYvQfgUuMQiPwk8gjYfFKmsnTU0iuzZU2mgutflyGz6ecbPU3z0N3Ww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743638921; c=relaxed/simple; bh=A4qOF8g/Lp0fNN70XKVNtD9pF/sKUksq0VFQkLxYtOA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=YR+D7PGCCczOGk8iUPlxoR5eUk5ZQElHLNwBJchD0ttmUjINKyKExVmre33NrDgrIR8Tu3DaACtIvOxBZdGyfAQTHDtmlhDm0iOEdeBK6l9KU9dQIhfgTN0VGt/Say4IChiG7img0Qgtf+IKhxBF4h8koaYlLvmjF1k5k2Enmqc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--pcc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Eem3MP+g; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--pcc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Eem3MP+g" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-2ff52e1c56fso434678a91.2 for ; Wed, 02 Apr 2025 17:08:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1743638919; x=1744243719; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=mEgmoeCU7ZoBbD/6q07yzTwvuV9KDxvtvsClWJ9QuF8=; b=Eem3MP+g4EtVriA43tI3xztih2frs8m0SDRAT+ey1GJCq69R56WsoDNa7zniFZMVvy KTWeByMWvOGbbcc/exEJD6vt5bEyvx+8l0TyGdt9/q+2jT1wPzqbPFj7d2oRPAUHs3De gilDD7Lv+QRNJnXKCVQSV94JHof+SU2XzOUWNxrzRVOty4X7PvMGUgX4KrzQS7rmXfFj poBBJRSPDN/EaDlPEKUYbrUAkM7eWdtKhVyg8avnPA5PnkR4lTMGW2EAG6qfZQiRrk2f CTcTTbP4jlFTycgG+uT2L4x0msLPH39IbNqgV2YUK5MDiWochrxuJfxa7hDFFKBgT08Q urQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1743638919; x=1744243719; 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=mEgmoeCU7ZoBbD/6q07yzTwvuV9KDxvtvsClWJ9QuF8=; b=Xxoggoid2YjGX1XMpQiwFj6k8JVDpLvsEVbpJXtGFPtUbMF4Kj+Z9SBGX65y0zxXou g7zvnr027PCpTYDalSlKMNI4TuWleWbCPMhqLv+aE1xzNuIVIPe+Askt3yZsMm38WL/g 19gpDD/qF5JGgXxuXSjxroiZOqAGKHJlMg4X/xAF+KmeW4PgdPSjk7JnQ+I31OIS9vWR w2FlH49078hvnBbbpvIr4p6vUNcAcvJv+/9gKzE1AIL+3JeQ1uv4D6nO5NiVT0ekdJVj /X71SsqdJ5ZuSlvHtXGeac3gTyOWnU/H/GFfd36EEiCmQKyK17jqWqs0Knf+woVuLXny ShvQ== X-Forwarded-Encrypted: i=1; AJvYcCViR6zitVoLlC7OS9209SxZFmE5K0VPNbjnMGqpS0/HVfxacNR5Mcr9fsIgoQCUsF28ov7wHuM=@vger.kernel.org X-Gm-Message-State: AOJu0YxrBhlwnX1dXPXo/FHs3lYa2oYfeDpTwhAQsOHFuJC5CewKzY1+ W5Km8RhTy63ZceM9trcbevXISoWHzrXqoej2VQiIw8fyJSi99CaTT0W1tYzBNbQb9w== X-Google-Smtp-Source: AGHT+IEn+KDt633hxPIy/Xv0o5YX2H1GlYC0LI3Wy6iiMYKkwRX/0697A1IGauH6w3mSOoDfNBnB/3U= X-Received: from pjbsu16.prod.google.com ([2002:a17:90b:5350:b0:2ea:9d23:79a0]) (user=pcc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:5241:b0:2ff:58a4:9db5 with SMTP id 98e67ed59e1d1-3056ef46f92mr5028152a91.30.1743638918950; Wed, 02 Apr 2025 17:08:38 -0700 (PDT) Date: Wed, 2 Apr 2025 17:06:59 -0700 In-Reply-To: <20250403000703.2584581-1-pcc@google.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250403000703.2584581-1-pcc@google.com> X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250403000703.2584581-2-pcc@google.com> Subject: [PATCH v5 1/2] string: Add load_unaligned_zeropad() code path to sized_strscpy() From: Peter Collingbourne To: Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Kees Cook , Andy Shevchenko , Andrey Konovalov , Catalin Marinas , Mark Rutland Cc: Peter Collingbourne , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" The call to read_word_at_a_time() in sized_strscpy() is problematic with MTE because it may trigger a tag check fault when reading across a tag granule (16 bytes) boundary. To make this code MTE compatible, let's start using load_unaligned_zeropad() on architectures where it is available (i.e. architectures that define CONFIG_DCACHE_WORD_ACCESS). Because load_unaligned_zeropad() takes care of page boundaries as well as tag granule boundaries, also disable the code preventing crossing page boundaries when using load_unaligned_zeropad(). Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/If4b22e43b5a4ca49726b4bf98ada827fdf755548 Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS") Cc: stable@vger.kernel.org --- v2: - new approach lib/string.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/lib/string.c b/lib/string.c index eb4486ed40d25..b632c71df1a50 100644 --- a/lib/string.c +++ b/lib/string.c @@ -119,6 +119,7 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count) if (count == 0 || WARN_ON_ONCE(count > INT_MAX)) return -E2BIG; +#ifndef CONFIG_DCACHE_WORD_ACCESS #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS /* * If src is unaligned, don't cross a page boundary, @@ -133,12 +134,14 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count) /* If src or dest is unaligned, don't do word-at-a-time. */ if (((long) dest | (long) src) & (sizeof(long) - 1)) max = 0; +#endif #endif /* - * read_word_at_a_time() below may read uninitialized bytes after the - * trailing zero and use them in comparisons. Disable this optimization - * under KMSAN to prevent false positive reports. + * load_unaligned_zeropad() or read_word_at_a_time() below may read + * uninitialized bytes after the trailing zero and use them in + * comparisons. Disable this optimization under KMSAN to prevent + * false positive reports. */ if (IS_ENABLED(CONFIG_KMSAN)) max = 0; @@ -146,7 +149,11 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count) while (max >= sizeof(unsigned long)) { unsigned long c, data; +#ifdef CONFIG_DCACHE_WORD_ACCESS + c = load_unaligned_zeropad(src+res); +#else c = read_word_at_a_time(src+res); +#endif if (has_zero(c, &data, &constants)) { data = prep_zero_mask(c, data, &constants); data = create_zero_mask(data); -- 2.49.0.472.ge94155a9ec-goog