unpack-trees: watch for out-of-range index position

It's possible in a case where the index file contains a tree extension
but no blobs within that tree exist for index_pos_by_traverse_info() to
segfault. If the name_entry passed into index_pos_by_traverse_info() has
no blobs inside, AND is alphabetically later than all blobs currently in
the index file, index_pos_by_traverse_info() will segfault. For example,
an index file which looks something like this:

  aaa#0
  bbb/aaa#0
  [Extensions]
  TREE: zzz

In this example, 'index_name_pos(..., "zzz/", ...)' will return '-4',
indicating that "zzz/" could be inserted at position 3. However, when
the checks which ensure that the insertion position of "zzz/" look for a
blob at that position beginning with "zzz/", the index cache is accessed
out of range, causing a segfault.

This kind of index state is not typically generated during user
operations, and is in fact an edge case of the state being checked for
in the conditional where it was added. However, since the entry for the
BUG() line is ambiguous, tell some additional context to help Git
developers debug the failure later. When we know the name of the dir we
were trying to look up, it becomes possible to examine the index file
in a hex util to determine what went wrong; the position gives a hint
about where to start looking.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 file changed
tree: 2f7c34962b20f2d7687c4abbb2ee4355039b0a7a
  1. .github/
  2. block-sha1/
  3. builtin/
  4. ci/
  5. compat/
  6. contrib/
  7. Documentation/
  8. ewah/
  9. git-gui/
  10. gitk-git/
  11. gitweb/
  12. mergetools/
  13. negotiator/
  14. perl/
  15. po/
  16. ppc/
  17. refs/
  18. sha1dc/
  19. sha256/
  20. t/
  21. templates/
  22. trace2/
  23. vcs-svn/
  24. xdiff/
  25. .clang-format
  26. .editorconfig
  27. .gitattributes
  28. .gitignore
  29. .gitmodules
  30. .mailmap
  31. .travis.yml
  32. .tsan-suppressions
  33. abspath.c
  34. aclocal.m4
  35. advice.c
  36. advice.h
  37. alias.c
  38. alias.h
  39. alloc.c
  40. alloc.h
  41. apply.c
  42. apply.h
  43. archive-tar.c
  44. archive-zip.c
  45. archive.c
  46. archive.h
  47. argv-array.c
  48. argv-array.h
  49. attr.c
  50. attr.h
  51. azure-pipelines.yml
  52. banned.h
  53. base85.c
  54. bisect.c
  55. bisect.h
  56. blame.c
  57. blame.h
  58. blob.c
  59. blob.h
  60. branch.c
  61. branch.h
  62. builtin.h
  63. bulk-checkin.c
  64. bulk-checkin.h
  65. bundle.c
  66. bundle.h
  67. cache-tree.c
  68. cache-tree.h
  69. cache.h
  70. chdir-notify.c
  71. chdir-notify.h
  72. check-builtins.sh
  73. check_bindir
  74. checkout.c
  75. checkout.h
  76. CODE_OF_CONDUCT.md
  77. color.c
  78. color.h
  79. column.c
  80. column.h
  81. combine-diff.c
  82. command-list.txt
  83. commit-graph.c
  84. commit-graph.h
  85. commit-reach.c
  86. commit-reach.h
  87. commit-slab-decl.h
  88. commit-slab-impl.h
  89. commit-slab.h
  90. commit.c
  91. commit.h
  92. common-main.c
  93. config.c
  94. config.h
  95. config.mak.dev
  96. config.mak.in
  97. config.mak.uname
  98. configure.ac
  99. connect.c
  100. connect.h
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  102. connected.h
  103. convert.c
  104. convert.h
  105. copy.c
  106. COPYING
  107. credential-cache--daemon.c
  108. credential-cache.c
  109. credential-store.c
  110. credential.c
  111. credential.h
  112. csum-file.c
  113. csum-file.h
  114. ctype.c
  115. daemon.c
  116. date.c
  117. decorate.c
  118. decorate.h
  119. delta-islands.c
  120. delta-islands.h
  121. delta.h
  122. detect-compiler
  123. diff-delta.c
  124. diff-lib.c
  125. diff-no-index.c
  126. diff.c
  127. diff.h
  128. diffcore-break.c
  129. diffcore-delta.c
  130. diffcore-order.c
  131. diffcore-pickaxe.c
  132. diffcore-rename.c
  133. diffcore.h
  134. dir-iterator.c
  135. dir-iterator.h
  136. dir.c
  137. dir.h
  138. editor.c
  139. entry.c
  140. environment.c
  141. exec-cmd.c
  142. exec-cmd.h
  143. fast-import.c
  144. fetch-negotiator.c
  145. fetch-negotiator.h
  146. fetch-pack.c
  147. fetch-pack.h
  148. fmt-merge-msg.h
  149. fsck.c
  150. fsck.h
  151. fsmonitor.c
  152. fsmonitor.h
  153. fuzz-commit-graph.c
  154. fuzz-pack-headers.c
  155. fuzz-pack-idx.c
  156. generate-cmdlist.sh
  157. gettext.c
  158. gettext.h
  159. git-add--interactive.perl
  160. git-archimport.perl
  161. git-bisect.sh
  162. git-compat-util.h
  163. git-cvsexportcommit.perl
  164. git-cvsimport.perl
  165. git-cvsserver.perl
  166. git-difftool--helper.sh
  167. git-filter-branch.sh
  168. git-instaweb.sh
  169. git-legacy-stash.sh
  170. git-merge-octopus.sh
  171. git-merge-one-file.sh
  172. git-merge-resolve.sh
  173. git-mergetool--lib.sh
  174. git-mergetool.sh
  175. git-p4.py
  176. git-parse-remote.sh
  177. git-quiltimport.sh
  178. git-rebase--preserve-merges.sh
  179. git-request-pull.sh
  180. git-send-email.perl
  181. git-sh-i18n.sh
  182. git-sh-setup.sh
  183. git-submodule.sh
  184. git-svn.perl
  185. GIT-VERSION-GEN
  186. git-web--browse.sh
  187. git.c
  188. git.rc
  189. gpg-interface.c
  190. gpg-interface.h
  191. graph.c
  192. graph.h
  193. grep.c
  194. grep.h
  195. hash.h
  196. hashmap.c
  197. hashmap.h
  198. help.c
  199. help.h
  200. hex.c
  201. http-backend.c
  202. http-fetch.c
  203. http-push.c
  204. http-walker.c
  205. http.c
  206. http.h
  207. ident.c
  208. imap-send.c
  209. INSTALL
  210. interdiff.c
  211. interdiff.h
  212. iterator.h
  213. json-writer.c
  214. json-writer.h
  215. khash.h
  216. kwset.c
  217. kwset.h
  218. levenshtein.c
  219. levenshtein.h
  220. LGPL-2.1
  221. line-log.c
  222. line-log.h
  223. line-range.c
  224. line-range.h
  225. linear-assignment.c
  226. linear-assignment.h
  227. list-objects-filter-options.c
  228. list-objects-filter-options.h
  229. list-objects-filter.c
  230. list-objects-filter.h
  231. list-objects.c
  232. list-objects.h
  233. list.h
  234. ll-merge.c
  235. ll-merge.h
  236. lockfile.c
  237. lockfile.h
  238. log-tree.c
  239. log-tree.h
  240. ls-refs.c
  241. ls-refs.h
  242. mailinfo.c
  243. mailinfo.h
  244. mailmap.c
  245. mailmap.h
  246. Makefile
  247. match-trees.c
  248. mem-pool.c
  249. mem-pool.h
  250. merge-blobs.c
  251. merge-blobs.h
  252. merge-recursive.c
  253. merge-recursive.h
  254. merge.c
  255. mergesort.c
  256. mergesort.h
  257. midx.c
  258. midx.h
  259. name-hash.c
  260. notes-cache.c
  261. notes-cache.h
  262. notes-merge.c
  263. notes-merge.h
  264. notes-utils.c
  265. notes-utils.h
  266. notes.c
  267. notes.h
  268. object-store.h
  269. object.c
  270. object.h
  271. oidmap.c
  272. oidmap.h
  273. oidset.c
  274. oidset.h
  275. pack-bitmap-write.c
  276. pack-bitmap.c
  277. pack-bitmap.h
  278. pack-check.c
  279. pack-objects.c
  280. pack-objects.h
  281. pack-revindex.c
  282. pack-revindex.h
  283. pack-write.c
  284. pack.h
  285. packfile.c
  286. packfile.h
  287. pager.c
  288. parse-options-cb.c
  289. parse-options.c
  290. parse-options.h
  291. patch-delta.c
  292. patch-ids.c
  293. patch-ids.h
  294. path.c
  295. path.h
  296. pathspec.c
  297. pathspec.h
  298. pkt-line.c
  299. pkt-line.h
  300. preload-index.c
  301. pretty.c
  302. pretty.h
  303. prio-queue.c
  304. prio-queue.h
  305. progress.c
  306. progress.h
  307. promisor-remote.c
  308. promisor-remote.h
  309. prompt.c
  310. prompt.h
  311. protocol.c
  312. protocol.h
  313. quote.c
  314. quote.h
  315. range-diff.c
  316. range-diff.h
  317. reachable.c
  318. reachable.h
  319. read-cache.c
  320. README.md
  321. rebase-interactive.c
  322. rebase-interactive.h
  323. ref-filter.c
  324. ref-filter.h
  325. reflog-walk.c
  326. reflog-walk.h
  327. refs.c
  328. refs.h
  329. refspec.c
  330. refspec.h
  331. remote-curl.c
  332. remote-testsvn.c
  333. remote.c
  334. remote.h
  335. replace-object.c
  336. replace-object.h
  337. repo-settings.c
  338. repository.c
  339. repository.h
  340. rerere.c
  341. rerere.h
  342. resolve-undo.c
  343. resolve-undo.h
  344. revision.c
  345. revision.h
  346. run-command.c
  347. run-command.h
  348. send-pack.c
  349. send-pack.h
  350. sequencer.c
  351. sequencer.h
  352. serve.c
  353. serve.h
  354. server-info.c
  355. setup.c
  356. sh-i18n--envsubst.c
  357. sha1-array.c
  358. sha1-array.h
  359. sha1-file.c
  360. sha1-lookup.c
  361. sha1-lookup.h
  362. sha1-name.c
  363. sha1dc_git.c
  364. sha1dc_git.h
  365. shallow.c
  366. shell.c
  367. shortlog.h
  368. sideband.c
  369. sideband.h
  370. sigchain.c
  371. sigchain.h
  372. split-index.c
  373. split-index.h
  374. stable-qsort.c
  375. strbuf.c
  376. strbuf.h
  377. streaming.c
  378. streaming.h
  379. string-list.c
  380. string-list.h
  381. sub-process.c
  382. sub-process.h
  383. submodule-config.c
  384. submodule-config.h
  385. submodule.c
  386. submodule.h
  387. symlinks.c
  388. tag.c
  389. tag.h
  390. tar.h
  391. tempfile.c
  392. tempfile.h
  393. thread-utils.c
  394. thread-utils.h
  395. tmp-objdir.c
  396. tmp-objdir.h
  397. trace.c
  398. trace.h
  399. trace2.c
  400. trace2.h
  401. trailer.c
  402. trailer.h
  403. transport-helper.c
  404. transport-internal.h
  405. transport.c
  406. transport.h
  407. tree-diff.c
  408. tree-walk.c
  409. tree-walk.h
  410. tree.c
  411. tree.h
  412. unicode-width.h
  413. unimplemented.sh
  414. unix-socket.c
  415. unix-socket.h
  416. unpack-trees.c
  417. unpack-trees.h
  418. upload-pack.c
  419. upload-pack.h
  420. url.c
  421. url.h
  422. urlmatch.c
  423. urlmatch.h
  424. usage.c
  425. userdiff.c
  426. userdiff.h
  427. utf8.c
  428. utf8.h
  429. varint.c
  430. varint.h
  431. version.c
  432. version.h
  433. versioncmp.c
  434. walker.c
  435. walker.h
  436. wildmatch.c
  437. wildmatch.h
  438. worktree.c
  439. worktree.h
  440. wrap-for-bin.sh
  441. wrapper.c
  442. write-or-die.c
  443. ws.c
  444. wt-status.c
  445. wt-status.h
  446. xdiff-interface.c
  447. xdiff-interface.h
  448. zlib.c
README.md

Build Status

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://public-inbox.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