From: Julian Andres Klode Date: Wed, 31 Aug 2016 15:01:04 +0000 (+0200) Subject: TagFile: Fix off-by-one errors in comment stripping X-Git-Tag: 1.3_rc4~13 X-Git-Url: https://git.saurik.com/apt.git/commitdiff_plain/923c592ceb6014b31ec751b97b3ed659fa3e88ae TagFile: Fix off-by-one errors in comment stripping Adding 1 to the value of d->End - current makes restLength one byte too long: If we pass memchr(current, ..., restLength) has thus undefined behavior. Also, reading the value of current has undefined behavior if current >= d->End, not only for current > d->End: Consider a string of length 1, that is d->End = d->Current + 1. We can only read at d->Current + 0, but d->Current + 1 is beyond the end of the string. This probably caused several inexplicable build failures on hurd-i386 in the past, and just now caused a build failure on Ubuntu's amd64 builder. Reported-By: valgrind --- diff --git a/apt-pkg/tagfile.cc b/apt-pkg/tagfile.cc index 3a3a3a04a..69148e08b 100644 --- a/apt-pkg/tagfile.cc +++ b/apt-pkg/tagfile.cc @@ -300,7 +300,7 @@ static void RemoveCommentsFromBuffer(pkgTagFilePrivate * const d) std::vector> good_parts; while (current <= d->End) { - size_t const restLength = (d->End - current) + 1; + size_t const restLength = (d->End - current); if (d->isCommentedLine == false) { current = static_cast(memchr(current, '#', restLength)); @@ -335,7 +335,7 @@ static void RemoveCommentsFromBuffer(pkgTagFilePrivate * const d) } ++current; // is the next line a comment, too? - if (current > d->End || *current != '#') + if (current >= d->End || *current != '#') { d->chunks.emplace_back(false, (current - bad_start)); good_start = current;