From patchwork Sat Mar 29 00:03:37 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Collingbourne X-Patchwork-Id: 14032552 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 CE6AEC3600C for ; Sat, 29 Mar 2025 00:09:22 +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; 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AJvYcCVpVdsEexCLDUCwq+Gb1dTVCZ1kAPxn/X/Pf3eCI+RztiydYJ+jZj7rKnr8ix3aVpAmr6313Pmaa72o+kYUQvQt@lists.infradead.org X-Gm-Message-State: AOJu0YxS6M+hGP2sbtMXwSPgP5EKb6L8QPqOWVaK3vwQWPtVAs+tz44n sD3yt4riPUY+bT9+l2/qW5fAU1y5I52juFhODeaZb8XW9uIMkiJyBVtRc92oJMRt/Q== X-Google-Smtp-Source: AGHT+IG1OCkWK6ACc2gjb+axSi3OGauLJByZEq2XzaKVmUmtuGmaBnSVPaf+lB7MT0QcfgqXjpACp1o= X-Received: from plrc9.prod.google.com ([2002:a17:902:aa49:b0:229:2f8a:aac5]) (user=pcc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:eb8d:b0:21f:564:80a4 with SMTP id d9443c01a7336-2292f9e5139mr16353845ad.33.1743206633220; Fri, 28 Mar 2025 17:03:53 -0700 (PDT) Date: Fri, 28 Mar 2025 17:03:37 -0700 In-Reply-To: <20250329000338.1031289-1-pcc@google.com> Mime-Version: 1.0 References: <20250329000338.1031289-1-pcc@google.com> X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250329000338.1031289-3-pcc@google.com> Subject: [PATCH v4 2/2] kasan: Add strscpy() test to trigger tag fault on arm64 From: Peter Collingbourne To: Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Kees Cook , Andy Shevchenko , Andrey Konovalov , Catalin Marinas , Mark Rutland Cc: Vincenzo Frascino , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Will Deacon , Peter Collingbourne X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250328_170354_973436_74C6E403 X-CRM114-Status: GOOD ( 14.80 ) 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 From: Vincenzo Frascino When we invoke strscpy() with a maximum size of N bytes, it assumes that: - It can always read N bytes from the source. - It always write N bytes (zero-padded) to the destination. On aarch64 with Memory Tagging Extension enabled if we pass an N that is bigger then the source buffer, it would previously trigger an MTE fault. Implement a KASAN KUnit test that triggers the issue with the previous implementation of read_word_at_a_time() on aarch64 with MTE enabled. Cc: Will Deacon Signed-off-by: Vincenzo Frascino Signed-off-by: Catalin Marinas Co-developed-by: Peter Collingbourne Signed-off-by: Peter Collingbourne Reviewed-by: Andrey Konovalov Link: https://linux-review.googlesource.com/id/If88e396b9e7c058c1a4b5a252274120e77b1898a --- v4: - clarify commit message - improve comment v3: - simplify test case v2: - rebased - fixed test failure mm/kasan/kasan_test_c.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c index 59d673400085f..655356df71fe6 100644 --- a/mm/kasan/kasan_test_c.c +++ b/mm/kasan/kasan_test_c.c @@ -1570,6 +1570,7 @@ static void kasan_memcmp(struct kunit *test) static void kasan_strings(struct kunit *test) { char *ptr; + char *src; size_t size = 24; /* @@ -1581,6 +1582,21 @@ static void kasan_strings(struct kunit *test) ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); + src = kmalloc(KASAN_GRANULE_SIZE, GFP_KERNEL | __GFP_ZERO); + strscpy(src, "f0cacc1a0000000", KASAN_GRANULE_SIZE); + + /* + * Make sure that strscpy() does not trigger KASAN if it overreads into + * poisoned memory. + * + * The expected size does not include the terminator '\0' + * so it is (KASAN_GRANULE_SIZE - 2) == + * KASAN_GRANULE_SIZE - ("initial removed character" + "\0"). + */ + KUNIT_EXPECT_EQ(test, KASAN_GRANULE_SIZE - 2, + strscpy(ptr, src + 1, KASAN_GRANULE_SIZE)); + + kfree(src); kfree(ptr); /*