gcc-plugins/stackleak: Exactly match strings instead of prefixes
Since STRING_CST may not be NUL terminated, strncmp() was used for check for equality. However, this may lead to mismatches for longer section names where the start matches the tested-for string. Test for exact equality by checking for the presences of NUL termination. Cc: Alexander Popov <alex.popov@linux.com> Signed-off-by: Kees Cook <keescook@chromium.org>
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@ -429,6 +429,23 @@ static unsigned int stackleak_cleanup_execute(void)
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return 0;
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}
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/*
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* STRING_CST may or may not be NUL terminated:
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* https://gcc.gnu.org/onlinedocs/gccint/Constant-expressions.html
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*/
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static inline bool string_equal(tree node, const char *string, int length)
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{
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if (TREE_STRING_LENGTH(node) < length)
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return false;
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if (TREE_STRING_LENGTH(node) > length + 1)
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return false;
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if (TREE_STRING_LENGTH(node) == length + 1 &&
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TREE_STRING_POINTER(node)[length] != '\0')
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return false;
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return !memcmp(TREE_STRING_POINTER(node), string, length);
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}
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#define STRING_EQUAL(node, str) string_equal(node, str, strlen(str))
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static bool stackleak_gate(void)
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{
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tree section;
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@ -438,13 +455,13 @@ static bool stackleak_gate(void)
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if (section && TREE_VALUE(section)) {
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section = TREE_VALUE(TREE_VALUE(section));
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if (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10))
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if (STRING_EQUAL(section, ".init.text"))
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return false;
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if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13))
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if (STRING_EQUAL(section, ".devinit.text"))
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return false;
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if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13))
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if (STRING_EQUAL(section, ".cpuinit.text"))
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return false;
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if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
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if (STRING_EQUAL(section, ".meminit.text"))
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return false;
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}
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