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The oid_array object uses an "int" to store the number of items and the
allocated size. It's rather unlikely for somebody to have more than 2^31
objects in a repository (the sha1's alone would be 40GB!), but if they
do, we'd overflow our alloc variable.
You can reproduce this case with something like:
git init repo
cd repo
# make a pack with 2^24 objects
perl -e '
my $nr = 2**24;
for (my $i = 0; $i < $nr; $i++) {
print "blob\n";
print "data 4\n";
print pack("N", $i);
}
' | git fast-import
# now make 256 copies of it; most of these objects will be duplicates,
# but oid_array doesn't de-dup until all values are read and it can
# sort the result.
cd .git/objects/pack/
pack=$(echo *.pack)
idx=$(echo *.idx)
for i in $(seq 0 255); do
# no need to waste disk space
ln "$pack" "pack-extra-$i.pack"
ln "$idx" "pack-extra-$i.idx"
done
# and now force an oid_array to store all of it
git cat-file --batch-all-objects --batch-check
which results in:
fatal: size_t overflow: 32 * 18446744071562067968
So the good news is that st_mult() sees the problem (the large number is
because our int wraps negative, and then that gets cast to a size_t),
doing the job it was meant to: bailing in crazy situations rather than
causing an undersized buffer.
But we should avoid hitting this case at all, and instead limit
ourselves based on what malloc() is willing to give us. We can easily do
that by switching to size_t.
The cat-file process above made it to ~120GB virtual set size before the
integer overflow (our internal hash storage is 32-bytes now in
preparation for sha256, so we'd expect ~128GB total needed, plus
potentially more to copy from one realloc'd block to another)). After
this patch (and about 130GB of RAM+swap), it does eventually read in the
whole set. No test for obvious reasons.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
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The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks