From 4f0cd4c218f11263359e36152030416e6e6184ab Mon Sep 17 00:00:00 2001 From: tabudz Date: Mon, 24 Feb 2025 15:41:01 +0800 Subject: [PATCH] Remove offset pointer optimization in inftrees.c. inftrees.c was subtracting an offset from a pointer to an array, in order to provide a pointer that allowed indexing starting at the offset. This is not compliant with the C standard, for which the behavior of a pointer decremented before its allocated memory is undefined. Per the recommendation of a security audit of the zlib code by Trail of Bits and TrustInSoft, in support of the Mozilla Foundation, this tiny optimization was removed, in order to avoid the possibility of undefined behavior. --- examples/ThirdPartyLibs/zlib/inftrees.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/examples/ThirdPartyLibs/zlib/inftrees.c b/examples/ThirdPartyLibs/zlib/inftrees.c index a7a8f01a7c..4de5cc4261 100644 --- a/examples/ThirdPartyLibs/zlib/inftrees.c +++ b/examples/ThirdPartyLibs/zlib/inftrees.c @@ -54,7 +54,7 @@ unsigned short FAR *work; code FAR *next; /* next available space in table */ const unsigned short FAR *base; /* base value table to use */ const unsigned short FAR *extra; /* extra bits table to use */ - int end; /* use base and extra for symbol > end */ + unsigned match; /* use base and extra for symbol >= match */ unsigned short count[MAXBITS + 1]; /* number of codes of each length */ unsigned short offs[MAXBITS + 1]; /* offsets in table for each length */ static const unsigned short lbase[31] = {/* Length codes 257..285 base */ @@ -184,19 +184,17 @@ unsigned short FAR *work; { case CODES: base = extra = work; /* dummy value--not used */ - end = 19; + match = 20; break; case LENS: base = lbase; - base -= 257; extra = lext; - extra -= 257; - end = 256; + match = 257; break; default: /* DISTS */ base = dbase; extra = dext; - end = -1; + match = 0; } /* initialize state for loop */ @@ -220,15 +218,15 @@ unsigned short FAR *work; { /* create table entry */ here.bits = (unsigned char)(len - drop); - if ((int)(work[sym]) < end) + if (work[sym] + 1 < match) { { here.op = (unsigned char)0; here.val = work[sym]; } - else if ((int)(work[sym]) > end) + else if (work[sym] >= match) { - here.op = (unsigned char)(extra[work[sym]]); - here.val = base[work[sym]]; + here.op = (unsigned char)(extra[work[sym] - match]); + here.val = base[work[sym] - match]; } else {