Git with broken hash generation to generate collisions between object IDs. Don't use this!
https://undefinedbehavior.de/posts/commit-vandalism/
4090511e40
When using a multi-pack bitmap, pack-objects will try to perform its
traversal using a call to `traverse_bitmap_commit_list()`, which calls
`add_object_entry_from_bitmap()` to add each object it finds to its
packing list.
This path can cause pack-objects to add objects from packs that don't
have open pack_fds on them, by avoiding a call to `is_pack_valid()`.
This is because we only call `is_pack_valid()` on the preferred pack (in
order to do verbatim reuse via `reuse_partial_packfile_from_bitmap()`)
and not others when loading a MIDX bitmap.
In this case, `add_object_entry_from_bitmap()` will check whether it
wants each object entry by calling `want_object_in_pack()`, which will
call `want_found_object` (since its caller already supplied a
`found_pack`). In most cases (particularly without `--local`, and when
`ignored_packed_keep_on_disk` and `ignored_packed_keep_in_core` are
both "0"), we'll take the entry from the pack contained in the MIDX
bitmap, all without an open pack_fd.
When we then try to use that entry later to assemble the actual pack,
we'll be susceptible to any simultaneous writers moving that pack out of
the way (e.g., due to a concurrent repack) without having an open file
descriptor, causing races that result in errors like:
remote: Enumerating objects: 1498802, done.
remote: fatal: packfile ./objects/pack/pack-e57d433b5a588daa37fbe946e2b28dfaec03a93e.pack cannot be accessed
remote: aborting due to possible repository corruption on the remote side.
This race can happen even with multi-pack bitmaps, since we may open a
MIDX bitmap that is being rewritten long before its packs are actually
unlinked.
Work around this by calling `is_pack_valid()` from within
`want_found_object()`, matching the behavior in
`want_object_in_pack_one()` (which has an analogous call). Most calls to
`is_pack_valid()` should be basically no-ops, since only the first call
requires us to open a file (subsequent calls realize the file is already
open, and return immediately).
Importantly, when `want_object_in_pack()` is given a non-NULL
`*found_pack`, but `want_found_object()` rejects the copy of the object
in that pack, we must reset `*found_pack` and `*found_offset` to NULL
and 0, respectively. Failing to do so could lead to other checks in
`want_object_in_pack()` (such as `want_object_in_pack_one()`) using the
same (invalid) pack as `*found_pack`, meaning that we don't call
`is_pack_valid()` because `p == *found_pack`. This can lead the caller
to believe it can use a copy of an object from an invalid pack.
An alternative approach to closing this race would have been to call
`is_pack_valid()` on _all_ packs in a multi-pack bitmap on load. This
has a couple of problems:
- it is unnecessarily expensive in the cases where we don't actually
need to open any packs (e.g., in `git rev-list --use-bitmap-index
--count`)
- more importantly, it means any time we would have hit this race,
we'll avoid using bitmaps altogether, leading to significant
slowdowns by forcing a full object traversal
Co-authored-by: Victoria Dye <vdye@github.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
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| block-sha1 | ||
| builtin | ||
| ci | ||
| compat | ||
| contrib | ||
| Documentation | ||
| ewah | ||
| git-gui | ||
| gitk-git | ||
| gitweb | ||
| mergetools | ||
| negotiator | ||
| perl | ||
| po | ||
| ppc | ||
| refs | ||
| reftable | ||
| sha1collisiondetection@855827c583 | ||
| sha1dc | ||
| sha256 | ||
| t | ||
| templates | ||
| trace2 | ||
| xdiff | ||
| .cirrus.yml | ||
| .clang-format | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
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| .mailmap | ||
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| abspath.c | ||
| aclocal.m4 | ||
| add-interactive.c | ||
| add-interactive.h | ||
| add-patch.c | ||
| advice.c | ||
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| alias.h | ||
| alloc.c | ||
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| attr.c | ||
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| banned.h | ||
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| branch.c | ||
| branch.h | ||
| builtin.h | ||
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| cbtree.c | ||
| cbtree.h | ||
| chdir-notify.c | ||
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| check-builtins.sh | ||
| checkout.c | ||
| checkout.h | ||
| chunk-format.c | ||
| chunk-format.h | ||
| CODE_OF_CONDUCT.md | ||
| color.c | ||
| color.h | ||
| column.c | ||
| column.h | ||
| combine-diff.c | ||
| command-list.txt | ||
| commit-graph.c | ||
| commit-graph.h | ||
| commit-reach.c | ||
| commit-reach.h | ||
| commit-slab-decl.h | ||
| commit-slab-impl.h | ||
| commit-slab.h | ||
| commit.c | ||
| commit.h | ||
| common-main.c | ||
| config.c | ||
| config.h | ||
| config.mak.dev | ||
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| configure.ac | ||
| connect.c | ||
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| convert.c | ||
| convert.h | ||
| copy.c | ||
| COPYING | ||
| credential.c | ||
| credential.h | ||
| csum-file.c | ||
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| ctype.c | ||
| daemon.c | ||
| date.c | ||
| decorate.c | ||
| decorate.h | ||
| delta-islands.c | ||
| delta-islands.h | ||
| delta.h | ||
| detect-compiler | ||
| diff-delta.c | ||
| diff-lib.c | ||
| diff-merges.c | ||
| diff-merges.h | ||
| diff-no-index.c | ||
| diff.c | ||
| diff.h | ||
| diffcore-break.c | ||
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| diffcore-order.c | ||
| diffcore-pickaxe.c | ||
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| diffcore.h | ||
| dir-iterator.c | ||
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| dir.c | ||
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| editor.c | ||
| entry.c | ||
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| environment.c | ||
| environment.h | ||
| exec-cmd.c | ||
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| fetch-negotiator.c | ||
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| fetch-pack.c | ||
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| fmt-merge-msg.c | ||
| fmt-merge-msg.h | ||
| fsck.c | ||
| fsck.h | ||
| fsmonitor.c | ||
| fsmonitor.h | ||
| fuzz-commit-graph.c | ||
| fuzz-pack-headers.c | ||
| fuzz-pack-idx.c | ||
| generate-cmdlist.sh | ||
| generate-configlist.sh | ||
| generate-hooklist.sh | ||
| gettext.c | ||
| gettext.h | ||
| git-add--interactive.perl | ||
| git-archimport.perl | ||
| git-bisect.sh | ||
| git-compat-util.h | ||
| git-curl-compat.h | ||
| git-cvsexportcommit.perl | ||
| git-cvsimport.perl | ||
| git-cvsserver.perl | ||
| git-difftool--helper.sh | ||
| git-filter-branch.sh | ||
| git-instaweb.sh | ||
| git-merge-octopus.sh | ||
| git-merge-one-file.sh | ||
| git-merge-resolve.sh | ||
| git-mergetool--lib.sh | ||
| git-mergetool.sh | ||
| git-p4.py | ||
| git-quiltimport.sh | ||
| git-request-pull.sh | ||
| git-send-email.perl | ||
| git-sh-i18n.sh | ||
| git-sh-setup.sh | ||
| git-submodule.sh | ||
| git-svn.perl | ||
| GIT-VERSION-GEN | ||
| git-web--browse.sh | ||
| git.c | ||
| git.rc | ||
| gpg-interface.c | ||
| gpg-interface.h | ||
| graph.c | ||
| graph.h | ||
| grep.c | ||
| grep.h | ||
| hash-lookup.c | ||
| hash-lookup.h | ||
| hash.h | ||
| hashmap.c | ||
| hashmap.h | ||
| help.c | ||
| help.h | ||
| hex.c | ||
| hook.c | ||
| hook.h | ||
| http-backend.c | ||
| http-fetch.c | ||
| http-push.c | ||
| http-walker.c | ||
| http.c | ||
| http.h | ||
| ident.c | ||
| imap-send.c | ||
| INSTALL | ||
| iterator.h | ||
| json-writer.c | ||
| json-writer.h | ||
| khash.h | ||
| kwset.c | ||
| kwset.h | ||
| levenshtein.c | ||
| levenshtein.h | ||
| LGPL-2.1 | ||
| line-log.c | ||
| line-log.h | ||
| line-range.c | ||
| line-range.h | ||
| linear-assignment.c | ||
| linear-assignment.h | ||
| list-objects-filter-options.c | ||
| list-objects-filter-options.h | ||
| list-objects-filter.c | ||
| list-objects-filter.h | ||
| list-objects.c | ||
| list-objects.h | ||
| list.h | ||
| ll-merge.c | ||
| ll-merge.h | ||
| lockfile.c | ||
| lockfile.h | ||
| log-tree.c | ||
| log-tree.h | ||
| ls-refs.c | ||
| ls-refs.h | ||
| mailinfo.c | ||
| mailinfo.h | ||
| mailmap.c | ||
| mailmap.h | ||
| Makefile | ||
| match-trees.c | ||
| mem-pool.c | ||
| mem-pool.h | ||
| merge-blobs.c | ||
| merge-blobs.h | ||
| merge-ort-wrappers.c | ||
| merge-ort-wrappers.h | ||
| merge-ort.c | ||
| merge-ort.h | ||
| merge-recursive.c | ||
| merge-recursive.h | ||
| merge.c | ||
| mergesort.c | ||
| mergesort.h | ||
| midx.c | ||
| midx.h | ||
| name-hash.c | ||
| notes-cache.c | ||
| notes-cache.h | ||
| notes-merge.c | ||
| notes-merge.h | ||
| notes-utils.c | ||
| notes-utils.h | ||
| notes.c | ||
| notes.h | ||
| object-file.c | ||
| object-name.c | ||
| object-store.h | ||
| object.c | ||
| object.h | ||
| oid-array.c | ||
| oid-array.h | ||
| oidmap.c | ||
| oidmap.h | ||
| oidset.c | ||
| oidset.h | ||
| oidtree.c | ||
| oidtree.h | ||
| pack-bitmap-write.c | ||
| pack-bitmap.c | ||
| pack-bitmap.h | ||
| pack-check.c | ||
| pack-objects.c | ||
| pack-objects.h | ||
| pack-revindex.c | ||
| pack-revindex.h | ||
| pack-write.c | ||
| pack.h | ||
| packfile.c | ||
| packfile.h | ||
| pager.c | ||
| parallel-checkout.c | ||
| parallel-checkout.h | ||
| parse-options-cb.c | ||
| parse-options.c | ||
| parse-options.h | ||
| patch-delta.c | ||
| patch-ids.c | ||
| patch-ids.h | ||
| path.c | ||
| path.h | ||
| pathspec.c | ||
| pathspec.h | ||
| pkt-line.c | ||
| pkt-line.h | ||
| preload-index.c | ||
| pretty.c | ||
| pretty.h | ||
| prio-queue.c | ||
| prio-queue.h | ||
| progress.c | ||
| progress.h | ||
| promisor-remote.c | ||
| promisor-remote.h | ||
| prompt.c | ||
| prompt.h | ||
| protocol-caps.c | ||
| protocol-caps.h | ||
| protocol.c | ||
| protocol.h | ||
| prune-packed.c | ||
| prune-packed.h | ||
| quote.c | ||
| quote.h | ||
| range-diff.c | ||
| range-diff.h | ||
| reachable.c | ||
| reachable.h | ||
| read-cache.c | ||
| README.md | ||
| rebase-interactive.c | ||
| rebase-interactive.h | ||
| rebase.c | ||
| rebase.h | ||
| ref-filter.c | ||
| ref-filter.h | ||
| reflog-walk.c | ||
| reflog-walk.h | ||
| refs.c | ||
| refs.h | ||
| refspec.c | ||
| refspec.h | ||
| RelNotes | ||
| remote-curl.c | ||
| remote.c | ||
| remote.h | ||
| replace-object.c | ||
| replace-object.h | ||
| repo-settings.c | ||
| repository.c | ||
| repository.h | ||
| rerere.c | ||
| rerere.h | ||
| reset.c | ||
| reset.h | ||
| resolve-undo.c | ||
| resolve-undo.h | ||
| revision.c | ||
| revision.h | ||
| run-command.c | ||
| run-command.h | ||
| SECURITY.md | ||
| send-pack.c | ||
| send-pack.h | ||
| sequencer.c | ||
| sequencer.h | ||
| serve.c | ||
| serve.h | ||
| server-info.c | ||
| setup.c | ||
| sh-i18n--envsubst.c | ||
| sha1dc_git.c | ||
| sha1dc_git.h | ||
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| shallow.h | ||
| shell.c | ||
| shortlog.h | ||
| sideband.c | ||
| sideband.h | ||
| sigchain.c | ||
| sigchain.h | ||
| simple-ipc.h | ||
| sparse-index.c | ||
| sparse-index.h | ||
| split-index.c | ||
| split-index.h | ||
| stable-qsort.c | ||
| strbuf.c | ||
| strbuf.h | ||
| streaming.c | ||
| streaming.h | ||
| string-list.c | ||
| string-list.h | ||
| strmap.c | ||
| strmap.h | ||
| strvec.c | ||
| strvec.h | ||
| sub-process.c | ||
| sub-process.h | ||
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| submodule-config.h | ||
| submodule.c | ||
| submodule.h | ||
| symlinks.c | ||
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| tag.h | ||
| tar.h | ||
| tempfile.c | ||
| tempfile.h | ||
| thread-utils.c | ||
| thread-utils.h | ||
| tmp-objdir.c | ||
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| trace2.h | ||
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| trailer.h | ||
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| transport.c | ||
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| tree.h | ||
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| unimplemented.sh | ||
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| unix-socket.h | ||
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| unix-stream-server.h | ||
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| upload-pack.c | ||
| upload-pack.h | ||
| url.c | ||
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| urlmatch.c | ||
| urlmatch.h | ||
| usage.c | ||
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| userdiff.h | ||
| utf8.c | ||
| utf8.h | ||
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| varint.h | ||
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| version.h | ||
| versioncmp.c | ||
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| walker.h | ||
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| worktree.h | ||
| wrap-for-bin.sh | ||
| wrapper.c | ||
| write-or-die.c | ||
| ws.c | ||
| wt-status.c | ||
| wt-status.h | ||
| xdiff-interface.c | ||
| xdiff-interface.h | ||
| zlib.c | ||
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.
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