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portable_strndup() must not read source string beyond NUL byte.

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POSIX strndup() does not read memory beyond NUL byte of the source
string.  Preserve this behavior in libexpat implementation to prevent
access violations and keep portability.
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Sebastian Pipping 2025-03-30 17:06:01 +02:00 • committed by Alexander Bluhm
parent 03ff328b5c
commit 5b9e8dc70c
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1 changed files with 10 additions and 1 deletions
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11
expat/tests/common.c
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@ -303,7 +303,14 @@ duff_reallocator(void *ptr, size_t size) {
return realloc(ptr, size);
}
// Portable remake of strndup(3) for C99; does not care about space efficiency
// Portable remake of strnlen(3) for C99
static size_t
portable_strnlen(const char *s, size_t maxlen) {
const char *const end = (const char *)memchr(s, '\0', maxlen);
return (end == NULL) ? maxlen : (size_t)(end - s);
}
// Portable remake of strndup(3) for C99
char *
portable_strndup(const char *s, size_t n) {
if ((s == NULL) || (n == SIZE_MAX)) {
@ -311,6 +318,8 @@ portable_strndup(const char *s, size_t n) {
return NULL;
}
n = portable_strnlen(s, n);
char *const buffer = (char *)malloc(n + 1);
if (buffer == NULL) {
errno = ENOMEM;