From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-il1-x134.google.com (mail-il1-x134.google.com [IPv6:2607:f8b0:4864:20::134]) by sourceware.org (Postfix) with ESMTPS id 148563858432 for ; Tue, 15 Feb 2022 17:23:42 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 148563858432 Received: by mail-il1-x134.google.com with SMTP id h11so15334885ilq.9 for ; Tue, 15 Feb 2022 09:23:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=LrDSsJ5KUQVTJ3fKaolRr5ke43OTR9OaB+pff2MHLt8=; b=RbJ213frKhJZT1x4fZrbZEGGtE6P/A9zLjYmac46en2x3UGot1LeLODBfduZwV2Vzy a29Xjhhr7fcYrtq2GCbE9HrKcjV/UfN68FqhnAyPI93G/AqqrAu70VzGRZ/bXMlV87xa mgNlwuySTTtPap2EZuy6bPgeuHjD9XvoWuhKGO1cQ7T7ZVMjaTVuNqP2Y7gBZfA2gEGT sJ8JJJpjdubBXRVXXs6T10Ps1mDGfM3ny33xEDilCbLv4KUVc1HKp4BhQkUzUCO6oDNT aEhqjdYhRy/nm+7Drr5Pv7pkG3OlLa6dgFQ+nzP4Xmhuq1ofS5zPGuStp/8EiTQFkuQ0 h3iA== X-Gm-Message-State: AOAM532bTdsat6hWuNxVuukzNmP1YadKwTu/8HcoDRC1ahf+C17kWZ0h mvJnH8a/4wEzbYwk5lJ8crUPqWC0C+c= X-Google-Smtp-Source: ABdhPJxnjTh3YStf6FmQQ9irNYjJqIWx7RqTVp5HbeirBMSqxNjY5Ctk6MZEc0WE22Ll1aXFVVdVlw== X-Received: by 2002:a92:d8c4:: with SMTP id l4mr55640ilo.61.1644945821256; Tue, 15 Feb 2022 09:23:41 -0800 (PST) Received: from localhost.localdomain (node-17-161.flex.volo.net. [76.191.17.161]) by smtp.googlemail.com with ESMTPSA id j14sm21566530ilc.62.2022.02.15.09.23.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Feb 2022 09:23:40 -0800 (PST) From: Noah Goldstein To: libc-alpha@sourceware.org Subject: [PATCH v3] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Date: Tue, 15 Feb 2022 11:23:36 -0600 Message-Id: <20220215172336.314600-1-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220215162829.282223-1-goldstein.w.n@gmail.com> References: <20220215162829.282223-1-goldstein.w.n@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Feb 2022 17:23:43 -0000 Logic can read before the start of `s1` / `s2` if both `s1` and `s2` are near the start of a page. To avoid having the result contimated by these comparisons the `strcmp` variants would mask off these comparisons. This was missing in the `strncmp` variants causing the bug. This commit adds the masking to `strncmp` so that out of range comparisons don't affect the result. test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as well a full xcheck on x86_64 linux. --- string/test-strncmp.c | 22 ++++++++++++++++++++++ sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 + sysdeps/x86_64/multiarch/strcmp-evex.S | 1 + 3 files changed, 24 insertions(+) diff --git a/string/test-strncmp.c b/string/test-strncmp.c index 831cb77893..090b61316c 100644 --- a/string/test-strncmp.c +++ b/string/test-strncmp.c @@ -423,6 +423,27 @@ check3 (void) } } +static void +check4 (void) +{ + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of + the end of the page. 2) For there to be no mismatch/null byte before the + first page cross. 3) For length (`n`) to be large enough for one string to + cross the page. And 4) for there to be either mismatch/null bytes before + the start of the strings. */ + + size_t size = 10; + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR)); + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR)); + int exp_result; + + STRCPY (s1, L ("tst-tlsmod%")); + STRCPY (s2, L ("tst-tls-manydynamic73mod")); + exp_result = SIMPLE_STRNCMP (s1, s2, size); + FOR_EACH_IMPL (impl, 0) + check_result (impl, s1, s2, size, exp_result); +} + static void check_overflow (void) { @@ -546,6 +567,7 @@ test_main (void) check1 (); check2 (); check3 (); + check4 (); printf ("%23s", ""); FOR_EACH_IMPL (impl, 0) diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S index 99e5349be8..07a5a2c889 100644 --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S @@ -661,6 +661,7 @@ L(ret8): # ifdef USE_AS_STRNCMP .p2align 4,, 10 L(return_page_cross_end_check): + andl %r10d, %ecx tzcntl %ecx, %ecx leal -VEC_SIZE(%rax, %rcx), %ecx cmpl %ecx, %edx diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S index 6f42e3155a..56d8c118e4 100644 --- a/sysdeps/x86_64/multiarch/strcmp-evex.S +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S @@ -689,6 +689,7 @@ L(ret8): # ifdef USE_AS_STRNCMP .p2align 4,, 10 L(return_page_cross_end_check): + andl %r10d, %ecx tzcntl %ecx, %ecx leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx # ifdef USE_AS_WCSCMP -- 2.25.1