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: 14021627 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 8B2DFC282EC for ; Tue, 18 Mar 2025 21:45:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=eTUn5qDH83alwoR8172wGnmaTD/nkQcDeotToQ/FQtU=; b=bkLX9sakTvqDveuQB9ePYNc6E4 ODgjGRveK2rbfCS9ZP+WAX+SFzs8IBq7X4NBtuxyblzcL0EpUPAoXEJhpNGrbNBWyCTOd6Z3LG142 hsY+Xxi/LI4dL9lAPTzjgXf5mVhEku84LH50P4k9ufk9fEvyZai+13ejwPRvkJdlqNAgw16ZmYOch VUn0skgopZEFHeWWAxnjjeqZFs07pSEZ0omtYD1ykJ5yZjsE8sfPpdYb1oMDIx+pDyIX2E2e8J9e2 ZhMlALcvp9mnP3huFuLuSvp2o5hh546suTyInJeA8st7aGXuAGtSFHNTS4BebkzGtiKz0/UyRHHtL koGVhEpw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tuek9-000000079ba-0pbD; Tue, 18 Mar 2025 21:45:01 +0000 Received: from mail-pl1-x649.google.com ([2607:f8b0:4864:20::649]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tuego-0000000790U-1mZn for linux-arm-kernel@lists.infradead.org; Tue, 18 Mar 2025 21:41:35 +0000 Received: by mail-pl1-x649.google.com with SMTP id d9443c01a7336-224192ff68bso89470445ad.1 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=lists.infradead.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=eNG6aCeomgHFsCpxR5pX00qtnbu4p8f+KdOMZa4tC9a4Reo4EK+9CjKBKr9EPJJXj0 U/HHXSOXVNfiEtlqjlrRI+CoycAyx+p4dytavWktISAxx7aqN+FaCpkloZKdMQ5mSeoF QZfv2zioVoopWKlnTlBvqqrjSMmZtqwxidXH4UNAaijKLFyl2mw5IEVCMOj1DLH7I66N e3t5Sz2onitsqH4mBTkAhLgptOijzDE2w7Au5DSk+2DrPXMXJDYkQSSGhOV7CauI9XDl eIE3hncpZ1u6SVuRRZPCHA9+lBgjJYeRvlTkHD+G+5DSMVEGnY08wFOMIVEHTjAA7xei Yk4w== 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=PfZQYtVgibvSYx5/bXbBx8SBtfR9069p58Qt1sav+sRy6nVrIEIxgHwM5/qtF6KDVg 6zdLv0B+3Zd6cJ0bKiyXevejc6cc2AhQjUcqcRjVe2I0T9fxshbotrSuMXB9o2v7AeB3 /u2zyBRWLnsxydxoCtOlZP1+MNyXleTjOggr3FMwI6u7sakBVFacneaas3UNcGzjAmOD 3S4FsV4yMyADnEPuYh2YXb6HlHtuOWrDd0msOy+ASHc+nWA1k1/Tmr//iSjebZFPPLZl +96h7YA0Rf0KGIbf5tVs2w3+Ta7fIP/DXspsn7uDL7GEWtqNdSjBi0w5oZVQ8+75PW43 7G1g== X-Forwarded-Encrypted: i=1; AJvYcCV/08x6fCe8DY6dV1htUp3vePJVxqbhpqNUmEO7+zmvVhbHL9wVgL8P2W4wSv7Parz+WJLFN71q/yoQDzkp/C5r@lists.infradead.org X-Gm-Message-State: AOJu0YznaoK7AsObnQs3zLM2Kp3voVZneUA0bWF0arUNdakWOTI6juHc NUnGmVI8bR0RSM6OUP5CNSLOUQjv/mz56hHTOx5pYfzDRLfv8IX8tmiyHU+wl4v09A== 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> 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250318_144134_462762_B78D22BE X-CRM114-Status: GOOD ( 14.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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);