dbd2b55cb7
The refs_resolve_ref_unsafe() function may return NULL even with a REF_ISSYMREF flag if a symref points to a broken ref. As a result, it's possible for find_shared_symref() to segfault when it passes NULL to strcmp(). This is hard to trigger for most code paths. We typically pass HEAD to the function as the symref to resolve, and programs like "git branch" will bail much earlier if HEAD isn't valid. I did manage to trigger it through one very obscure sequence: # You have multiple notes refs which conflict. git notes add -m base git notes --ref refs/notes/foo add -m foo # There's left-over cruft in NOTES_MERGE_REF that # makes it a broken symref (in this case we point # to a syntactically invalid ref). echo "ref: refs/heads/master.lock" >.git/NOTES_MERGE_REF # You try to merge the notes. We read the broken value in # order to complain that another notes-merge is # in-progress, but we segfault in find_shared_symref(). git notes merge refs/notes/foo This is obviously silly and almost certainly impossible to trigger accidentally, but it does show that the bug is triggerable from at least one code path. In addition, it would trigger if we saw a transient filesystem error when resolving the pointed-to ref. We can fix this by treating NULL the same as a non-matching symref. Arguably we'd prefer to know if a symref points to "refs/heads/foo", but "refs/heads/foo" is broken. But refs_resolve_ref_unsafe() isn't capable of giving us that information, so this is the best we can do. 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-.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://public-inbox.org/git/, http://marc.info/?l=git and other archival sites.
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