72 lines
2.7 KiB
Diff
72 lines
2.7 KiB
Diff
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From 6a043145ca6e9c55184013841a67b2fef87e44c0 Mon Sep 17 00:00:00 2001
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From: Mark Adler <madler@alumni.caltech.edu>
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Date: Wed, 21 Sep 2016 23:35:50 -0700
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Subject: [PATCH] Remove offset pointer optimization in inftrees.c.
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inftrees.c was subtracting an offset from a pointer to an array,
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in order to provide a pointer that allowed indexing starting at
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the offset. This is not compliant with the C standard, for which
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the behavior of a pointer decremented before its allocated memory
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is undefined. Per the recommendation of a security audit of the
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zlib code by Trail of Bits and TrustInSoft, in support of the
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Mozilla Foundation, this tiny optimization was removed, in order
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to avoid the possibility of undefined behavior.
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---
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inftrees.c | 18 ++++++++----------
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1 file changed, 8 insertions(+), 10 deletions(-)
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diff --git a/inftrees.c b/inftrees.c
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index 22fcd66..0d2670d 100644
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--- a/inftrees.c
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+++ b/inftrees.c
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@@ -54,7 +54,7 @@ unsigned short FAR *work;
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code FAR *next; /* next available space in table */
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const unsigned short FAR *base; /* base value table to use */
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const unsigned short FAR *extra; /* extra bits table to use */
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- int end; /* use base and extra for symbol > end */
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+ unsigned match; /* use base and extra for symbol >= match */
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unsigned short count[MAXBITS+1]; /* number of codes of each length */
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unsigned short offs[MAXBITS+1]; /* offsets in table for each length */
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static const unsigned short lbase[31] = { /* Length codes 257..285 base */
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@@ -181,19 +181,17 @@ unsigned short FAR *work;
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switch (type) {
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case CODES:
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base = extra = work; /* dummy value--not used */
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- end = 19;
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+ match = 20;
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break;
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case LENS:
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base = lbase;
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- base -= 257;
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extra = lext;
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- extra -= 257;
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- end = 256;
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+ match = 257;
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break;
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default: /* DISTS */
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base = dbase;
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extra = dext;
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- end = -1;
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+ match = 0;
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}
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/* initialize state for loop */
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@@ -216,13 +214,13 @@ unsigned short FAR *work;
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for (;;) {
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/* create table entry */
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here.bits = (unsigned char)(len - drop);
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- if ((int)(work[sym]) < end) {
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+ if (work[sym] + 1 < match) {
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here.op = (unsigned char)0;
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here.val = work[sym];
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}
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- else if ((int)(work[sym]) > end) {
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- here.op = (unsigned char)(extra[work[sym]]);
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- here.val = base[work[sym]];
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+ else if (work[sym] >= match) {
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+ here.op = (unsigned char)(extra[work[sym] - match]);
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+ here.val = base[work[sym] - match];
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}
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else {
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here.op = (unsigned char)(32 + 64); /* end of block */
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