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Fix undefined behaviour and sign extension issues in kstrtok

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Prevent read beyond the end of sep if it's an empty string.

Change to internally use unsigned char to avoid unwanted sign
extension on platforms where 'char' is signed.

Fix undefined behaviour where pointers were made to the element
before the start of `str`:
https://www.securecoding.cert.org/confluence/display/c/ARR30-C.+Do+not+form+or+use+out-of-bounds+pointers+or+array+subscripts
This commit is contained in:
Rob Davies 2018-01-10 17:05:57 +00:00
parent efd09f0a00
commit 6b83413b34
1 changed files with 8 additions and 7 deletions
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15
kstring.c
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@ -34,28 +34,29 @@ int ksprintf(kstring_t *s, const char *fmt, ...)
return l;
}
char *kstrtok(const char *str, const char *sep, ks_tokaux_t *aux)
char *kstrtok(const char *str, const char *sep_in, ks_tokaux_t *aux)
{
const char *p, *start;
const unsigned char *p, *start, *sep = (unsigned char *) sep_in;
if (sep) { // set up the table
if (str == 0 && aux->finished) return 0; // no need to set up if we have finished
aux->finished = 0;
if (sep[1]) {
if (sep[0] && sep[1]) {
aux->sep = -1;
aux->tab[0] = aux->tab[1] = aux->tab[2] = aux->tab[3] = 0;
for (p = sep; *p; ++p) aux->tab[*p>>6] |= 1ull<<(*p&0x3f);
} else aux->sep = sep[0];
}
if (aux->finished) return 0;
else if (str) aux->p = str - 1, aux->finished = 0;
else if (str) start = (unsigned char *) str, aux->finished = 0;
else start = (unsigned char *) aux->p + 1;
if (aux->sep < 0) {
for (p = start = aux->p + 1; *p; ++p)
for (p = start; *p; ++p)
if (aux->tab[*p>>6]>>(*p&0x3f)&1) break;
} else {
for (p = start = aux->p + 1; *p; ++p)
for (p = start; *p; ++p)
if (*p == aux->sep) break;
}
aux->p = p; // end of token
aux->p = (const char *) p; // end of token
if (*p == 0) aux->finished = 1; // no more tokens
return (char*)start;
}