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Index: usr.bin/compress/zopen.c
===================================================================
--- usr.bin/compress/zopen.c (revision 225020)
+++ usr.bin/compress/zopen.c (working copy)
@@ -486,7 +486,7 @@ zread(void *cookie, char *rbp, int num)
block_compress = maxbits & BLOCK_MASK;
maxbits &= BIT_MASK;
maxmaxcode = 1L << maxbits;
- if (maxbits > BITS) {
+ if (maxbits > BITS || maxbits < 12) {
errno = EFTYPE;
return (-1);
}
@@ -513,17 +513,28 @@ zread(void *cookie, char *rbp, int num)
for (code = 255; code >= 0; code--)
tab_prefixof(code) = 0;
clear_flg = 1;
- free_ent = FIRST - 1;
- if ((code = getcode(zs)) == -1) /* O, untimely death! */
- break;
+ free_ent = FIRST;
+ oldcode = -1;
+ continue;
}
incode = code;
- /* Special case for KwKwK string. */
+ /* Special case for kWkWk string. */
if (code >= free_ent) {
+ if (code > free_ent || oldcode == -1) {
+ /* Bad stream. */
+ errno = EINVAL;
+ return (-1);
+ }
*stackp++ = finchar;
code = oldcode;
}
+ /*
+ * The above condition ensures that code < free_ent.
+ * The construction of tab_prefixof in turn guarantees that
+ * each iteration decreases code and therefore stack usage is
+ * bound by 1 << BITS - 256.
+ */
/* Generate output characters in reverse order. */
while (code >= 256) {
@@ -540,7 +551,7 @@ middle: do {
} while (stackp > de_stack);
/* Generate the new entry. */
- if ((code = free_ent) < maxmaxcode) {
+ if ((code = free_ent) < maxmaxcode && oldcode != -1) {
tab_prefixof(code) = (u_short) oldcode;
tab_suffixof(code) = finchar;
free_ent = code + 1;
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