Fix integer overflow in _sdsMakeRoomFor (CVE-2021-41099)
The existing overflow checks handled the greedy growing, but didn't handle
a case where the addition of the header size is what causes the overflow.
@@ -239,7 +239,7 @@ void sdsclear(sds s) {
sds _sdsMakeRoomFor(sds s, size_t addlen, int greedy) {
void *sh, *newsh;
size_t avail = sdsavail(s);
- size_t len, newlen;
+ size_t len, newlen, reqlen;
char type, oldtype = s[-1] & SDS_TYPE_MASK;
int hdrlen;
size_t usable;
@@ -249,7 +249,7 @@ sds _sdsMakeRoomFor(sds s, size_t addlen, int greedy) {
len = sdslen(s);
sh = (char*)s-sdsHdrSize(oldtype);
- newlen = (len+addlen);
+ reqlen = newlen = (len+addlen);
assert(newlen > len); /* Catch size_t overflow */
if (greedy == 1) {
if (newlen < SDS_MAX_PREALLOC)
@@ -266,7 +266,7 @@ sds _sdsMakeRoomFor(sds s, size_t addlen, int greedy) {
if (type == SDS_TYPE_5) type = SDS_TYPE_8;
hdrlen = sdsHdrSize(type);
- assert(hdrlen + newlen + 1 > len); /* Catch size_t overflow */
+ assert(hdrlen + newlen + 1 > reqlen); /* Catch size_t overflow */
if (oldtype==type) {
newsh = s_realloc_usable(sh, hdrlen+newlen+1, &usable);
if (newsh == NULL) return NULL;
