From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) by sourceware.org (Postfix) with ESMTPS id 5946A3858D33 for ; Tue, 31 Jan 2023 22:43:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 5946A3858D33 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-oi1-x22f.google.com with SMTP id r205so14183077oib.9 for ; Tue, 31 Jan 2023 14:43:08 -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=Q5j4JuIFuX4O5tzxYbG26aoPQRtV+id7SitJQLTRdVw=; b=TpsQoPuufZhpjnChIFX4NrnwvBPOpQ2+9pPlRbjFLmAEt3etPcTtwQ6X1NAFcwvJWo 63c/PNqYvC5BNh70LRc5qBwspS9n7LX3vEPFBMeZif1QY1cTVP8FaXy/ZAAh/zyEfv9/ OJYsVqsOWqOK2/aeoaGNILGtMzI7lhEs50vefe8fTnrofTQdv44iYZQu42p/mmCp3dHJ S6ELB5AHgQMxoLq+gYrR/YK/w04SMyGXqsVw959ClIh74oEz8gFEgsAEwm2ogEOMh5fF ZgesjStwq2kXv8fBXgg6I0rcMWFEQKju3TGhZG83Ij1Kl5ueeTSs10uyjQjxwoQh3pLQ kwlQ== 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=Q5j4JuIFuX4O5tzxYbG26aoPQRtV+id7SitJQLTRdVw=; b=6+2Cm8+0aBbhjV121RY5I7O6k804Z6ef6XhT4z3HNfu2aUelWTe+U1je6NQyJ9fBen 1MocrhQwvwZ8IEbUiBpMjpdJ/0MfG8eM9HEFvaui0hhqUxGPXTJYSELNQ0eEPRZqgIXI GZVh9HYZSj0whXx5AN33twu9L9oa2RexJ/b08zbzfMlbeUEfhxNL5sVzzoYzdC/yyIs7 qtO6aPN7T5c4v7pojxtvQJEi+vQe25zgIUciQ+xtJOHvesURrZhwMDixWQeA3RbtwHee dCyBspKCkdPnnsL9X4LnhWe9rwxo3yePjwC1ILDF7NSLS5D5YsxCj7C37lBt9dvyQIk3 8e1g== X-Gm-Message-State: AO0yUKWiHFypx5YpahL6o0vRFftNMj9kAFRIsPaKTByd1/0WAFRe7219 9OjLHlUgz3SQWwvZzB5Kfhba/kt4Gvri6vHXBPar2Bfp X-Google-Smtp-Source: AK7set8eEzboVLYA8GzPLAewVmfLEuur4yDOGRglOc1Zc2dL5NlPUQXd9x141JNZqiK/Z9aPmFWpDcPCIohGz9jXtPI= X-Received: by 2002:aca:2317:0:b0:35b:c6c4:7a33 with SMTP id e23-20020aca2317000000b0035bc6c47a33mr24359oie.266.1675204987406; Tue, 31 Jan 2023 14:43:07 -0800 (PST) MIME-Version: 1.0 References: <20230131213655.4033602-1-goldstein.w.n@gmail.com> In-Reply-To: From: "H.J. Lu" Date: Tue, 31 Jan 2023 14:42:31 -0800 Message-ID: Subject: Re: [PATCH v1] x86: Fix strncat-avx2.S when `src` has no null-term [BZ #30065] To: Noah Goldstein Cc: libc-alpha@sourceware.org, carlos@systemhalted.org Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3022.9 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 2:37 PM Noah Goldstein wrote: > > 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. But it is incorrect to read beyond the limit even if there is a 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. -- H.J.