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commit bfdb731438206b0f70fe7afa890681155c30b419
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Author: Stefan Liebler <stli@linux.ibm.com>
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Date: Wed Nov 27 12:35:40 2019 +0100
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S390: Fix handling of needles crossing a page in strstr z15 ifunc-variant. [BZ #25226]
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If the specified needle crosses a page-boundary, the s390-z15 ifunc variant of
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strstr truncates the needle which results in invalid results.
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This is fixed by loading the needle beyond the page boundary to v18 instead of v16.
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The bug is sometimes observable in test-strstr.c in check1 and check2 as the
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haystack and needle is stored on stack. Thus the needle can be on a page boundary.
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check2 is now extended to test haystack / needles located on stack, at end of page
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and on two pages.
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This bug was introduced with commit 6f47401bd5fc71209219779a0426170a9a7395b0
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("S390: Add arch13 strstr ifunc variant.") and is already released in glibc 2.30.
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diff --git a/string/test-strstr.c b/string/test-strstr.c
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index 5861b01b73e4c315..e9e14c1ee605516e 100644
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--- a/string/test-strstr.c
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+++ b/string/test-strstr.c
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@@ -138,16 +138,45 @@ check1 (void)
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static void
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check2 (void)
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{
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- const char s1[] = ", enable_static, \0, enable_shared, ";
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+ const char s1_stack[] = ", enable_static, \0, enable_shared, ";
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+ const size_t s1_byte_count = 18;
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+ const char *s2_stack = &(s1_stack[s1_byte_count]);
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+ const size_t s2_byte_count = 18;
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char *exp_result;
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- char *s2 = (void *) buf1 + page_size - 18;
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+ const size_t page_size_real = getpagesize ();
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- strcpy (s2, s1);
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- exp_result = stupid_strstr (s1, s1 + 18);
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+ /* Haystack at end of page. The following page is protected. */
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+ char *s1_page_end = (void *) buf1 + page_size - s1_byte_count;
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+ strcpy (s1_page_end, s1_stack);
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+
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+ /* Haystack which crosses a page boundary.
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+ Note: page_size is at least 2 * getpagesize. See test_init. */
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+ char *s1_page_cross = (void *) buf1 + page_size_real - 8;
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+ strcpy (s1_page_cross, s1_stack);
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+
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+ /* Needle at end of page. The following page is protected. */
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+ char *s2_page_end = (void *) buf2 + page_size - s2_byte_count;
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+ strcpy (s2_page_end, s2_stack);
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+
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+ /* Needle which crosses a page boundary.
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+ Note: page_size is at least 2 * getpagesize. See test_init. */
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+ char *s2_page_cross = (void *) buf2 + page_size_real - 8;
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+ strcpy (s2_page_cross, s2_stack);
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+
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+ exp_result = stupid_strstr (s1_stack, s2_stack);
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FOR_EACH_IMPL (impl, 0)
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{
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- check_result (impl, s1, s1 + 18, exp_result);
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- check_result (impl, s2, s1 + 18, exp_result);
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+ check_result (impl, s1_stack, s2_stack, exp_result);
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+ check_result (impl, s1_stack, s2_page_end, exp_result);
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+ check_result (impl, s1_stack, s2_page_cross, exp_result);
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+
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+ check_result (impl, s1_page_end, s2_stack, exp_result);
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+ check_result (impl, s1_page_end, s2_page_end, exp_result);
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+ check_result (impl, s1_page_end, s2_page_cross, exp_result);
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+
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+ check_result (impl, s1_page_cross, s2_stack, exp_result);
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+ check_result (impl, s1_page_cross, s2_page_end, exp_result);
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+ check_result (impl, s1_page_cross, s2_page_cross, exp_result);
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}
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}
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diff --git a/sysdeps/s390/strstr-arch13.S b/sysdeps/s390/strstr-arch13.S
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index 929b026adfeba740..faa969849e09c2e1 100644
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--- a/sysdeps/s390/strstr-arch13.S
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+++ b/sysdeps/s390/strstr-arch13.S
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@@ -164,7 +164,7 @@ ENTRY(STRSTR_ARCH13)
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vfenezb %v19,%v18,%v18 /* Search zero in loaded needle bytes. */
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veclb %v19,%v21 /* Zero index <= max loaded byte index? */
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jle .Lneedle_loaded /* -> v18 contains full needle. */
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- vl %v16,0(%r3) /* Load needle beyond page boundary. */
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+ vl %v18,0(%r3) /* Load needle beyond page boundary. */
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vfenezb %v19,%v18,%v18
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j .Lneedle_loaded
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END(STRSTR_ARCH13)
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