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76 lines
2.8 KiB
76 lines
2.8 KiB
commit 5373c90f2ea3c3fa9931a684c9b81c648dfbe8d7 |
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Author: Noah Goldstein <goldstein.w.n@gmail.com> |
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Date: Tue Feb 15 20:27:21 2022 -0600 |
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x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] |
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Logic can read before the start of `s1` / `s2` if both `s1` and `s2` |
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are near the start of a page. To avoid having the result contimated by |
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these comparisons the `strcmp` variants would mask off these |
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comparisons. This was missing in the `strncmp` variants causing |
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the bug. This commit adds the masking to `strncmp` so that out of |
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range comparisons don't affect the result. |
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test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as |
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well a full xcheck on x86_64 linux. |
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Reviewed-by: H.J. Lu <hjl.tools@gmail.com> |
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(cherry picked from commit e108c02a5e23c8c88ce66d8705d4a24bb6b9a8bf) |
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diff --git a/string/test-strncmp.c b/string/test-strncmp.c |
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index 97e831d88fd24316..56e23670ae7f90e4 100644 |
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--- a/string/test-strncmp.c |
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+++ b/string/test-strncmp.c |
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@@ -438,13 +438,23 @@ check3 (void) |
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static void |
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check4 (void) |
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{ |
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- const CHAR *s1 = L ("abc"); |
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- CHAR *s2 = STRDUP (s1); |
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+ /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of |
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+ the end of the page. 2) For there to be no mismatch/null byte before the |
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+ first page cross. 3) For length (`n`) to be large enough for one string to |
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+ cross the page. And 4) for there to be either mismatch/null bytes before |
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+ the start of the strings. */ |
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+ |
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+ size_t size = 10; |
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+ size_t addr_mask = (getpagesize () - 1) ^ (sizeof (CHAR) - 1); |
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+ CHAR *s1 = (CHAR *)(buf1 + (addr_mask & 0xffa)); |
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+ CHAR *s2 = (CHAR *)(buf2 + (addr_mask & 0xfed)); |
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+ int exp_result; |
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+ STRCPY (s1, L ("tst-tlsmod%")); |
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+ STRCPY (s2, L ("tst-tls-manydynamic73mod")); |
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+ exp_result = SIMPLE_STRNCMP (s1, s2, size); |
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FOR_EACH_IMPL (impl, 0) |
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- check_result (impl, s1, s2, SIZE_MAX, 0); |
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- |
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- free (s2); |
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+ check_result (impl, s1, s2, size, exp_result); |
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} |
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int |
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diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S |
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index cdded412a70bad10..f9bdc5ccd03aa1f9 100644 |
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--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S |
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+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S |
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@@ -661,6 +661,7 @@ L(ret8): |
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# ifdef USE_AS_STRNCMP |
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.p2align 4,, 10 |
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L(return_page_cross_end_check): |
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+ andl %r10d, %ecx |
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tzcntl %ecx, %ecx |
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leal -VEC_SIZE(%rax, %rcx), %ecx |
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cmpl %ecx, %edx |
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diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S |
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index ed56af8ecdad48b2..0dfa62bd149c02b4 100644 |
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--- a/sysdeps/x86_64/multiarch/strcmp-evex.S |
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+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S |
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@@ -689,6 +689,7 @@ L(ret8): |
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# ifdef USE_AS_STRNCMP |
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.p2align 4,, 10 |
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L(return_page_cross_end_check): |
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+ andl %r10d, %ecx |
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tzcntl %ecx, %ecx |
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leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx |
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# ifdef USE_AS_WCSCMP
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