From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ej1-x62b.google.com (mail-ej1-x62b.google.com [IPv6:2a00:1450:4864:20::62b]) by sourceware.org (Postfix) with ESMTPS id 7BD763858D33 for ; Tue, 31 Jan 2023 22:37:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 7BD763858D33 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-ej1-x62b.google.com with SMTP id bk15so46031877ejb.9 for ; Tue, 31 Jan 2023 14:37:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=Mz34nnlpRxXTbSEM6z64QuogMOlsPx8LlZml3KBzk0Q=; b=BBzQDuDD6Oc+NVGQjxqQt/aVpARiV3956RGO/ZbfA1T/hSNsJQqlISGRWFvLLLZfcs ck8ewudv0ywfPl0NQCIRoMwFxsSceZNTgzASYljOyzjlxxZlfVdjeVFktjDxwj31z7Dv qmiB5Q8XKRjCADBLt7JIb9zNCe/uHZVuaJmV379oC2UYWfqNvQud3UmHES3sq9Imwtes 9uk4N2KZ28l2puUS9EoqB7Gp9PdQlQiUK7vsFnGsJ/NFmwBlD69Aqw6swh/1BZ+3uwEa jrRY23nez4NYXo0ecz1uWRpQnmxozPGZtRvkYXMmua/vnd07U+7RxEkziWT4k/z5qSz0 8LBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Mz34nnlpRxXTbSEM6z64QuogMOlsPx8LlZml3KBzk0Q=; b=S2oipTLEdEeQ1M4Gh/3/GKa70uxl1gXrBiIo88t5gHtnKC5sWObtwJf5oqhzb/NgzZ pZoi51Z01++0bZqa3dvOH7xph6w4utUqHUPtdrgK5cFWyjaQB04yGVKb5oAoN7CZ8hHu 2ocPkPV2UmQPCiqVZDalBJLNUyudHwpZbY3Oe/68EuN66hPqNUvV5OuTaufTkdvQg2/3 OWxKM6ggrlLmejX+uXLiOEwZFqz21zBd/Y/r0WkpIElmIwoIP8aBPlrIOd942fqnc3+F Ya9s6lnmeRn4+w1tJq0qdXaEwWt2XZVmYCqnol+V47H8SIyoQB44HKnRN3513UmG3qW5 k+2Q== X-Gm-Message-State: AO0yUKWiFgEfl0X0pw48oWD2vw1D1+kObf0ItasdB3Mfz7dEVs4A4syf t5Wc/jyLvOwGAFT49DsaifLANHUQh3yr49iOrUI= X-Google-Smtp-Source: AK7set9u6ecJQw1tJlRNNqva/nfI4YnZLfrxTtv9FSzW6ThDn7QUxn+XosEG/z2rd73vra3SiCeT6A7eFCgpGlyE/zA= X-Received: by 2002:a17:907:9917:b0:878:5f93:e797 with SMTP id ka23-20020a170907991700b008785f93e797mr15458ejc.4.1675204636712; Tue, 31 Jan 2023 14:37:16 -0800 (PST) MIME-Version: 1.0 References: <20230131213655.4033602-1-goldstein.w.n@gmail.com> In-Reply-To: From: Noah Goldstein Date: Tue, 31 Jan 2023 16:37:05 -0600 Message-ID: Subject: Re: [PATCH v1] x86: Fix strncat-avx2.S when `src` has no null-term [BZ #30065] To: "H.J. Lu" Cc: libc-alpha@sourceware.org, carlos@systemhalted.org Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-9.7 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 autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Tue, Jan 31, 2023 at 4:29 PM H.J. Lu wrote: > > On Tue, Jan 31, 2023 at 1:37 PM Noah Goldstein wrote: > > > > Two issue: > > > > 1) Zero-length check is doing: > > ``` > > test %rdx, %rdx > > jl L(zero_len) > > ``` > > which doesn't actually check zero (was at some point `decq` and the > > flag never got updated). > > > > The fix is just make the flag `jle` i.e: > > ``` > > test %rdx, %rdx > > jle L(zero_len) > > ``` > > > > 2) Length check in page-cross case checking if we should continue is > > doing: > > ``` > > cmpq %r8, %rdx > > jb L(page_cross_small) > > ``` > > which means we will continue searching for null-term if length ends at > > the end of a page and there was no null-term in `src`. > > It is not purely about null-term. strncat shouldn't read beyond the limit. > In this case, src may point to PROT_NONE memory. > If there was a null-term the later check: ``` shll $CHAR_SIZE, %ecx jz L(page_cross_continue) ``` would catch it, this can only occur if there is no null-term. > > The fix is to make the flag: > > ``` > > cmpq %r8, %rdx > > jbe L(page_cross_small) > > ``` > > --- > > string/test-strncat.c | 25 ++++++++++++++++++++++++- > > sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++-- > > 2 files changed, 26 insertions(+), 3 deletions(-) > > > > diff --git a/string/test-strncat.c b/string/test-strncat.c > > index e03d329e1c..c0cde206ee 100644 > > --- a/string/test-strncat.c > > +++ b/string/test-strncat.c > > @@ -28,6 +28,7 @@ > > # define CHAR char > > # define UCHAR unsigned char > > # define SIMPLE_STRNCAT simple_strncat > > +# define STRNLEN strnlen > > # define STRLEN strlen > > # define MEMSET memset > > # define MEMCPY memcpy > > @@ -40,6 +41,7 @@ > > # define CHAR wchar_t > > # define UCHAR wchar_t > > # define SIMPLE_STRNCAT simple_wcsncat > > +# define STRNLEN wcsnlen > > # define STRLEN wcslen > > # define MEMSET wmemset > > # define MEMCPY wmemcpy > > @@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n) > > return; > > } > > > > - size_t len = STRLEN (src); > > + size_t len = STRNLEN (src, n); > > if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0) > > > { > > error (0, 0, "Incorrect concatenation in function %s", > > @@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n) > > } > > } > > > > +static void > > +do_test_src_no_nullterm_bz30065 (void) > > +{ > > + /* NB: "src does not need to be null-terminated if it contains n or more > > + * bytes." */ > > + CHAR *s1, *s2; > > + size_t bound = page_size / sizeof (CHAR); > > + s1 = (CHAR *) (buf1 + BUF1PAGES * page_size); > > + s2 = (CHAR *) buf2; > > + MEMSET (s1 - bound, -1, bound); > > + for (size_t n = 0; n < bound; ++n) > > + { > > + FOR_EACH_IMPL (impl, 0) > > + { > > + s2[0] = '\0'; > > + do_one_test (impl, s2, s1 - n, n); > > + } > > + } > > +} > > + > > static void > > do_test (size_t align1, size_t align2, size_t len1, size_t len2, > > size_t n, int max_char) > > @@ -372,6 +394,7 @@ test_main (void) > > > > do_random_tests (); > > do_overflow_tests (); > > + do_test_src_no_nullterm_bz30065 (); > > return ret; > > } > > > > diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S > > index b380e8e11c..c2ff202238 100644 > > --- a/sysdeps/x86_64/multiarch/strncat-avx2.S > > +++ b/sysdeps/x86_64/multiarch/strncat-avx2.S > > @@ -66,7 +66,7 @@ ENTRY(STRNCAT) > > salq $2, %rdx > > # else > > test %rdx, %rdx > > - jl L(zero_len) > > + jle L(zero_len) > > # endif > > vpxor %VZERO_128, %VZERO_128, %VZERO_128 > > > > @@ -387,7 +387,7 @@ L(page_cross): > > subl %esi, %r8d > > andl $(VEC_SIZE - 1), %r8d > > cmpq %r8, %rdx > > - jb L(page_cross_small) > > + jbe L(page_cross_small) > > > > /* Optimizing more aggressively for space as this is very cold > > code. This saves 2x cache lines. */ > > -- > > 2.34.1 > > > > > -- > H.J.