From 2d4f26e5cfda682f9ce61444b81533b83f6381af Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Tue, 20 Sep 2022 17:58:04 -0700 Subject: [PATCH] x86: Fix wcsnlen-avx2 page cross length comparison [BZ #29591] Previous implementation was adjusting length (rsi) to match bytes (eax), but since there is no bound to length this can cause overflow. Fix is to just convert the byte-count (eax) to length by dividing by sizeof (wchar_t) before the comparison. Full check passes on x86-64 and build succeeds w/ and w/o multiarch. (cherry picked from commit b0969fa53a28b4ab2159806bf6c99a98999502ee) --- string/test-strnlen.c | 60 +++++++++++++++++--------- sysdeps/x86_64/multiarch/strlen-avx2.S | 7 +-- 2 files changed, 41 insertions(+), 26 deletions(-) diff --git a/string/test-strnlen.c b/string/test-strnlen.c index a1a6746cc9..ca34352b0d 100644 --- a/string/test-strnlen.c +++ b/string/test-strnlen.c @@ -75,7 +75,7 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char) { size_t i; - align &= 63; + align &= (getpagesize () / sizeof (CHAR) - 1); if ((align + len) * sizeof (CHAR) >= page_size) return; @@ -92,32 +92,50 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char) static void do_overflow_tests (void) { - size_t i, j, len; + size_t i, j, al_idx, repeats, len; const size_t one = 1; uintptr_t buf_addr = (uintptr_t) buf1; + const size_t alignments[] = { 0, 1, 7, 9, 31, 33, 63, 65, 95, 97, 127, 129 }; - for (i = 0; i < 750; ++i) + for (al_idx = 0; al_idx < sizeof (alignments) / sizeof (alignments[0]); + al_idx++) { - do_test (0, i, SIZE_MAX - i, BIG_CHAR); - do_test (0, i, i - buf_addr, BIG_CHAR); - do_test (0, i, -buf_addr - i, BIG_CHAR); - do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR); - do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR); + for (repeats = 0; repeats < 2; ++repeats) + { + size_t align = repeats ? (getpagesize () - alignments[al_idx]) + : alignments[al_idx]; + align /= sizeof (CHAR); + for (i = 0; i < 750; ++i) + { + do_test (align, i, SIZE_MAX, BIG_CHAR); - len = 0; - for (j = 8 * sizeof(size_t) - 1; j ; --j) - { - len |= one << j; - do_test (0, i, len - i, BIG_CHAR); - do_test (0, i, len + i, BIG_CHAR); - do_test (0, i, len - buf_addr - i, BIG_CHAR); - do_test (0, i, len - buf_addr + i, BIG_CHAR); + do_test (align, i, SIZE_MAX - i, BIG_CHAR); + do_test (align, i, i - buf_addr, BIG_CHAR); + do_test (align, i, -buf_addr - i, BIG_CHAR); + do_test (align, i, SIZE_MAX - buf_addr - i, BIG_CHAR); + do_test (align, i, SIZE_MAX - buf_addr + i, BIG_CHAR); - do_test (0, i, ~len - i, BIG_CHAR); - do_test (0, i, ~len + i, BIG_CHAR); - do_test (0, i, ~len - buf_addr - i, BIG_CHAR); - do_test (0, i, ~len - buf_addr + i, BIG_CHAR); - } + len = 0; + for (j = 8 * sizeof (size_t) - 1; j; --j) + { + len |= one << j; + do_test (align, i, len, BIG_CHAR); + do_test (align, i, len - i, BIG_CHAR); + do_test (align, i, len + i, BIG_CHAR); + do_test (align, i, len - buf_addr - i, BIG_CHAR); + do_test (align, i, len - buf_addr + i, BIG_CHAR); + + do_test (align, i, ~len - i, BIG_CHAR); + do_test (align, i, ~len + i, BIG_CHAR); + do_test (align, i, ~len - buf_addr - i, BIG_CHAR); + do_test (align, i, ~len - buf_addr + i, BIG_CHAR); + + do_test (align, i, -buf_addr, BIG_CHAR); + do_test (align, i, j - buf_addr, BIG_CHAR); + do_test (align, i, -buf_addr - j, BIG_CHAR); + } + } + } } } diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S b/sysdeps/x86_64/multiarch/strlen-avx2.S index 45e08e64d6..8cfb7391b0 100644 --- a/sysdeps/x86_64/multiarch/strlen-avx2.S +++ b/sysdeps/x86_64/multiarch/strlen-avx2.S @@ -542,14 +542,11 @@ L(return_vzeroupper): L(cross_page_less_vec): tzcntl %eax, %eax # ifdef USE_AS_WCSLEN - /* NB: Multiply length by 4 to get byte count. */ - sall $2, %esi + /* NB: Divide by 4 to convert from byte-count to length. */ + shrl $2, %eax # endif cmpq %rax, %rsi cmovb %esi, %eax -# ifdef USE_AS_WCSLEN - shrl $2, %eax -# endif VZEROUPPER_RETURN # endif