From patchwork Tue Mar 18 21:40:32 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Collingbourne X-Patchwork-Id: 14021606 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 D6D6B2063CB for ; Tue, 18 Mar 2025 21:41:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742334095; cv=none; b=dqmU/1SrQpiERU6PYQI7pps8ZCrScUoqCj3Dg7oIBRDqxFWcV3Jl+6OOlE5/qO6GZ6yYAlKvNU6m5apGN1dTn6WesKZsvxzdrr0BJJ2F2bAOuTvHS1jvLdYd+Q6UZHubfwdXEnV48vK0Dpp1ufnwHWSDBTOHHgD1TZX2uEuHeb4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742334095; c=relaxed/simple; bh=48tNNYVxNbJIhapHHVTjKQnmA5ByjfhX/glfPRAKIhc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=POuY45mg3/Lo6ELbq1hld07kvSeodtVYdKOo0LzhDBCrxlW6ue97LzPImzGcbjSwBEKlsGdr0ZGo6tOHOeb/33tVbin6KVR2gKP5A80IY7ufJ6Q7UJI7fzrjIprnaBPKvdupfFZTuCr/PDQnqvRPAcymqFys3WtINQ36lh9SBxw= 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=E+0JuCPu; arc=none smtp.client-ip=209.85.214.202 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="E+0JuCPu" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-225ab228a37so86775355ad.2 for ; Tue, 18 Mar 2025 14:41:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1742334093; x=1742938893; 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=eTUn5qDH83alwoR8172wGnmaTD/nkQcDeotToQ/FQtU=; b=E+0JuCPuXCTRQpxwuJCoPOuxF5kCEkC/7dh9RpTVY1vd36GHCre9gUgN5wIA20WDmh v9ah15eJ4BiIeGZ/MXE7wXesI/NjKWY2vivmuKO18oZfYhqC+iLAqXljJrQ2AJnVipNN TppDy357MnlZBUkqmlLwfdx6yobFatF7Dnubot0usBH9Cve4k+UtMD6hAPS8NtBw2dkk CO0+agWZuIznwDGLeO0reg59qWzpmwpQTpJZa79dQhJwP34sJ3fDc2F78LJIJX+uTNKW 7/Z94xujnNdvrEmTR4RF3eg7QrL4B+KX3qL+XyFShFhCfyF4M07YhPjuDbpE4sI243jD A4FA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1742334093; x=1742938893; 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=eTUn5qDH83alwoR8172wGnmaTD/nkQcDeotToQ/FQtU=; b=sGtupLBNIWaSmDiMc0o1574E6jYq/XXB8J4PdZWTCK8Xb+GED//dsIkhli1x6MkGhL 92NC1dLQq/D//BCj+X6dn5TqnveO58f57NwCuwkJsRvSUFAtBn4l/xlBaG0tg1ElULgT byGhfJDcpTnJyOpGqECGDkgOtUZSdbHtaAnYWY+7JUN3Tm1vwaQfugbktSuwOTX1JyXw JZWliGvZR+GgsABVWpwDqajJtp88qGdI2CufzRdtjFfYRkXygxf5hA/TaokxZmUyYa4N /4URJXPvs+K5xRvrsQra2rIjUmCDvZASvLD2NGI+94eOiUDLlylNZJQmo6LwKpzHTX10 oZXw== X-Forwarded-Encrypted: i=1; AJvYcCUnKBYDf00U6VLcpk/v0jUKlBOLrI2weDo772DxFRBq4f/qf6V4l/Sq9UVARAafCeEkFD0FdMl1jyMRfyQD@vger.kernel.org X-Gm-Message-State: AOJu0YzuVUOc7LZEVY6+iDFw1K9jJ6N7+3NhS1AW/C9bRuFMJqi4TXAB LZolMZy3qybqHb0GRq00hyGUZMNRw7kWsyOjMz4U/9fBC08qLYAJE7xLCY1dBJDipw== X-Google-Smtp-Source: AGHT+IG/QGxbxUqv2YDIjQQv/YN/p4GQJhFMy09dmHyQiNHhErBBFph57AE76+yZ/pqecPFGYqZrens= X-Received: from plsu3.prod.google.com ([2002:a17:902:bf43:b0:223:f487:afc6]) (user=pcc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2412:b0:223:3ef1:a30a with SMTP id d9443c01a7336-22649a57c52mr3056545ad.45.1742334093068; Tue, 18 Mar 2025 14:41:33 -0700 (PDT) Date: Tue, 18 Mar 2025 14:40:32 -0700 In-Reply-To: <20250318214035.481950-1-pcc@google.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250318214035.481950-1-pcc@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250318214035.481950-2-pcc@google.com> Subject: [PATCH v2 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 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);