Make sure nSelectors is not out of range
nSelectors is used in a loop from 0 to nSelectors to access selectorMtf
which is
UChar selectorMtf[BZ_MAX_SELECTORS];
so if nSelectors is bigger than BZ_MAX_SELECTORS it'll do an invalid memory
access
Fixes out of bounds access discovered while fuzzying karchive
This was reported as CVE-2019-12900
BZ2_decompress in decompress.c in bzip2 through 1.0.6 has an
out-of-bounds write when there are many selectors.
diff --git a/decompress.c b/decompress.c
index ab6a624..f3db91d 100644
--- a/decompress.c
+++ b/decompress.c
@@ -287,7 +287,7 @@
GET_BITS(BZ_X_SELECTOR_1, nGroups, 3);
if (nGroups < 2 || nGroups > 6) RETURN(BZ_DATA_ERROR);
GET_BITS(BZ_X_SELECTOR_2, nSelectors, 15);
- if (nSelectors < 1) RETURN(BZ_DATA_ERROR);
+ if (nSelectors < 1 || nSelectors > BZ_MAX_SELECTORS) RETURN(BZ_DATA_ERROR);
for (i = 0; i < nSelectors; i++) {
j = 0;
while (True) {
