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XCOFF archives use a bi-directional linked list for file members. So one member points to both the previous member and the next member. Members may not be sequentially ordered in the file. This of course is over-engineered nonsense and an attractive target for fuzzers. (There is even a free list of members!) The testcase in PR28423 is an XCOFF archive with one member pointing to itself, which results in lots of bad behaviour. For example, "ar t" never terminates. The use-after-free with "objdump -r" happens like this: The first archive element is opened, its symbols are read and "canonicalized" for objdump, then relocations are read and printed. Those relocations use the canonicalized symbols, and also happen to be cached by the coff bfd backend support. objdump frees the symbols. The next archive element is then opened. This must be done before the first element is closed, because finding the next element uses data held in the currect element. Unfortunately the next element happens to be the original, so we aren't opening, we're reopening a bfd which has cached data. When the relocations are printed they use the cached copy containing references to the freed canonical symbols. This patch adds a little sanity checking to the XCOFF "open next archive file" support, so that it rejects archive members pointing at themselves. That is sufficient to cure this problem. Anything more is overkill. If someone deliberately fuzzes an XCOFF archive with an element loop then reports an "ar" bug when it runs forever, they will find their bug report closed WONTFIX. PR 28423 * coff-rs6000.c (_bfd_xcoff_read_ar_hdr): Save size occupied by member name in areltdata.extra_size. (_bfd_xcoff_openr_next_archived_file): Sanity check nextoff. * coff64-rs6000.c (xcoff64_openr_next_archived_file): Call _bfd_xcoff_openr_next_archived_file.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.