aa962fef27
If Git's client-side parsing of an upload-pack response (so git-fetch or ls-remote) sees multiple instances of a single capability, it can enter an infinite loop due to a bug in advancing the "offset" parameter in the parser. This bug can't happen between a client and server of the same Git version. The client bug is in parse_feature_value() when the caller passes in an offset parameter. And that only happens when the v0 protocol is parsing "symref" and "object-format" capabilities, via next_server_feature_value(). But Git has never produced multiple object-format capabilities, and it stopped producing multiple symref values ind007dbf7d6(Revert "upload-pack: send non-HEAD symbolic refs", 2013-11-18). However, upload-pack did produce multiple symref entries for a while, and they are valid. Plus other implementations, such as Dulwich will still do so. So we should handle them. And even if we do not expect it, it is obviously a bug for the parser to enter an infinite loop. The bug itself is pretty simple. Commit2c6a403d96(connect: add function to parse multiple v1 capability values, 2020-05-25) added the "offset" parameter, which is used as both an in- and out-parameter. When parsing the first "symref" capability, *offset will be 0 on input, and after parsing the capability, we set *offset to an index just past the value by taking a pointer difference "(value + end) - feature_list". But on the second call, now *offset is set to that larger index, which lets us skip past the first "symref" capability. However, we do so by incrementing feature_list. That means our pointer difference is now too small; it is counting from where we resumed parsing, not from the start of the original feature_list pointer. And because we incremented feature_list only inside our function, and not the caller, that increment is lost next time the function is called. One solution would be to account for those skipped bytes by incrementing *offset, rather than assigning to it. But wait, there's more! We also increment feature_list if we have a near-miss. Say we are looking for "symref" and find "almost-symref". In that case we'll point feature_list to the "y" in "almost-symref" and restart our search. But that again means our offset won't be correct, as it won't account for the bytes between the start of the string and that "y". So instead, let's just record the beginning of the feature_list string in a separate pointer that we never touch. That offset we take in and return is meant to be using that point as a base, and now we'll do so consistently. Since the bug can't be reproduced using the current version of git-upload-pack, we'll instead hard-code an input which triggers the problem. Before this patch it loops forever re-parsing the second symref entry. Now we check both that it finishes, and that it parses both entries correctly (a case we could not test at all before). We don't need to worry about testing v2 here; it communicates the capabilities in a completely different way, and doesn't use this code at all. There are tests earlier in t5512 that are meant to cover this (they don't, but we'll address that in a future patch). Reported-by: Jonas Haag <jonas@lophus.org> 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