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When a commit appears in more than one pseudo-merge group, its entry in the commit lookup table has the high bit set in its offset field, indicating that the offset points to an "extended" table containing the set of pseudo-merges for that commit. There are three bugs in this path: * The `next_ext` offset in `write_pseudo_merges()` undercounts the per-entry size of the lookup table (8 vs. 12 bytes). * `nth_pseudo_merge_ext()` calls `read_pseudo_merge_commit_at()` on a pseudo-merge bitmap offset, misinterpreting it as a 12-byte commit table entry. * The error check after `pseudo_merge_ext_at()` in `apply_pseudo_merges_for_commit()` tests `< -1` instead of `< 0`, silently swallowing errors from `error()`. The first bug is on the write side: each commit lookup entry contains a 4- and 8-byte unsigned value for a total of 12 bytes, but the calculation assumes that the entry only contains 8 bytes of data. This makes `next_ext` too small, so the extended-table offsets that get written point into the middle of the non-extended lookup table rather than past it. The reader then interprets non-extended lookup data as extended entries, producing garbage. The second bug is on the read side and is independently fatal: even with a correctly positioned extended table, `nth_pseudo_merge_ext()` feeds the offset it reads (which points at pseudo-merge bitmap data) to `read_pseudo_merge_commit_at()`. That function tries to parse 12 bytes as a `pseudo_merge_commit` struct, clobbering `merge->pseudo_merge_ofs` with whatever happens to be at that location. The caller only needs `pseudo_merge_ofs`, so the fix is to store the offset directly rather than re-parsing a commit table entry. The `commit_pos` field is left untouched, retaining the value that `find_pseudo_merge()` set earlier. The third bug is latent. With the first two fixes applied, the extended table is correctly written and read, so `pseudo_merge_ext_at()` does not fail during normal operation. The `< -1` vs `< 0` distinction only matters when the bitmap file is corrupt or truncated, in which case the error would be silently ignored and the code would proceed with uninitialized data. Signed-off-by: Taylor Blau <me@ttaylorr.com> 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.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc 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.adoc
(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 to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://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