You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
91 lines
3.0 KiB
91 lines
3.0 KiB
7 months ago
|
From e108c02a5e23c8c88ce66d8705d4a24bb6b9a8bf Mon Sep 17 00:00:00 2001
|
||
|
|
From: Noah Goldstein <goldstein.w.n@gmail.com>
|
||
|
|
Date: Tue, 15 Feb 2022 20:27:21 -0600
|
||
|
|
Subject: [PATCH] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
|
||
|
|
Content-type: text/plain; charset=UTF-8
|
||
|
|
|
||
|
|
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.
|
||
|
|
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
|
||
|
|
---
|
||
|
|
string/test-strncmp.c | 23 +++++++++++++++++++++++
|
||
|
|
sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
|
||
|
|
sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
|
||
|
|
3 files changed, 25 insertions(+)
|
||
|
|
|
||
|
|
diff --git a/string/test-strncmp.c b/string/test-strncmp.c
|
||
|
|
index 927a6daa..e61fffd9 100644
|
||
|
|
--- a/string/test-strncmp.c
|
||
|
|
+++ b/string/test-strncmp.c
|
||
|
|
@@ -403,6 +403,28 @@ check2 (void)
|
||
|
|
free (s2);
|
||
|
|
}
|
||
|
|
|
||
|
|
+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;
|
||
|
|
+ size_t addr_mask = (getpagesize () - 1) ^ (sizeof (CHAR) - 1);
|
||
|
|
+ CHAR *s1 = (CHAR *)(buf1 + (addr_mask & 0xffa));
|
||
|
|
+ CHAR *s2 = (CHAR *)(buf2 + (addr_mask & 0xfed));
|
||
|
|
+ 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
|
||
|
|
check3 (void)
|
||
|
|
{
|
||
|
|
@@ -445,6 +467,7 @@ 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 04675aa4..179cc0e3 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 ed56af8e..0dfa62bd 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
|
||
|
|
--
|
||
|
|
GitLab
|
||
|
|
|