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From b0969fa53a28b4ab2159806bf6c99a98999502ee Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
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.
Conflict:adapt context.
Reference:https://sourceware.org/git/?p=glibc.git;a=commit;h=b0969fa53a28b4ab2159806bf6c99a98999502ee
Full check passes on x86-64 and build succeeds w/ and w/o multiarch.
---
string/test-strnlen.c | 70 +++++++++++++++-----------
sysdeps/x86_64/multiarch/strlen-avx2.S | 7 +--
2 files changed, 43 insertions(+), 34 deletions(-)
diff --git a/string/test-strnlen.c b/string/test-strnlen.c
index 4a9375112a..5cbaf4b734 100644
--- a/string/test-strnlen.c
+++ b/string/test-strnlen.c
@@ -73,7 +73,7 @@ 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;
@@ -90,36 +90,50 @@ 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);
-
- 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 (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 (0, i, -buf_addr, BIG_CHAR);
- do_test (0, i, j - buf_addr, BIG_CHAR);
- do_test (0, i, -buf_addr - j, 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);
+
+ 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);
+
+ 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 0593fb303b..b9b58ef599 100644
--- a/sysdeps/x86_64/multiarch/strlen-avx2.S
+++ b/sysdeps/x86_64/multiarch/strlen-avx2.S
@@ -544,14 +544,11 @@ 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
--
2.33.0
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