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We check the size of chunks with fixed records by multiplying the width of each record by the number of commits in the file. Like: if (chunk_size != g->num_commits * GRAPH_DATA_WIDTH) If this multiplication overflows, we may not notice a chunk is too small (which could later lead to out-of-bound reads). In the current code this is only possible for the CDAT chunk, but the reasons are quite subtle. We compute g->num_commits by dividing the size of the OIDL chunk by the hash length (since it consists of a bunch of hashes). So we know that any size_t multiplication that uses a value smaller than the hash length cannot overflow. And the CDAT records are the only ones that are larger (the others are just 4-byte records). So it's worth fixing all of these, to make it clear that they're not subject to overflow (without having to reason about seemingly unrelated code). The obvious thing to do is add an st_mult(), like: if (chunk_size != st_mult(g->num_commits, GRAPH_DATA_WIDTH)) And that certainly works, but it has one downside: if we detect an overflow, we'll immediately die(). But the commit graph is an optional file; if we run into other problems loading it, we'll generally return an error and fall back to accessing the full objects. Using st_mult() means a malformed file will abort the whole process. So instead, we can do a division like this: if (chunk_size / GRAPH_DATA_WIDTH != g->num_commits) where there's no possibility of overflow. We do lose a little bit of precision; due to integer division truncation we'd allow up to an extra GRAPH_DATA_WIDTH-1 bytes of data in the chunk. That's OK. Our main goal here is making sure we don't have too _few_ bytes, which would cause an out-of-bounds read (we could actually replace our "!=" with "<", but I think it's worth being a little pedantic, as a large mismatch could be a sign of other problems). I didn't add a test here. We'd need to generate a very large graph file in order to get g->num_commits large enough to cause an overflow. And a later patch in this series will use this same division technique in a way that is much easier to trigger in the tests. 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 and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org (not the Git list). The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
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