f751097be3
In a sparse index it is possible for the tree that is being verified
to be freed while it is being verified. This happens when the index is
sparse but the cache tree is not and index_name_pos() looks up a path
from the cache tree that is a descendant of a sparse index entry. That
triggers a call to ensure_full_index() which frees the cache tree that
is being verified. Carrying on trying to verify the tree after this
results in a use-after-free bug. Instead restart the verification if a
sparse index is converted to a full index. This bug is triggered by a
call to reset_head() in "git rebase --apply". Thanks to René Scharfe
and Derrick Stolee for their help analyzing the problem.
==74345==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000001b20 at pc 0x557cbe82d3a2 bp 0x7ffdfee08090 sp 0x7ffdfee08080
READ of size 4 at 0x606000001b20 thread T0
#0 0x557cbe82d3a1 in verify_one /home/phil/src/git/cache-tree.c:863
#1 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#2 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#3 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#4 0x557cbe830a2b in cache_tree_verify /home/phil/src/git/cache-tree.c:910
#5 0x557cbea53741 in write_locked_index /home/phil/src/git/read-cache.c:3250
#6 0x557cbeab7fdd in reset_head /home/phil/src/git/reset.c:87
#7 0x557cbe72147f in cmd_rebase builtin/rebase.c:2074
#8 0x557cbe5bd151 in run_builtin /home/phil/src/git/git.c:461
#9 0x557cbe5bd151 in handle_builtin /home/phil/src/git/git.c:714
#10 0x557cbe5c0503 in run_argv /home/phil/src/git/git.c:781
#11 0x557cbe5c0503 in cmd_main /home/phil/src/git/git.c:912
#12 0x557cbe5bad28 in main /home/phil/src/git/common-main.c:52
#13 0x7fdd4b82eb24 in __libc_start_main (/usr/lib/libc.so.6+0x27b24)
#14 0x557cbe5bcb8d in _start (/home/phil/src/git/git+0x1b9b8d)
0x606000001b20 is located 0 bytes inside of 56-byte region [0x606000001b20,0x606000001b58)
freed by thread T0 here:
#0 0x7fdd4bacff19 in __interceptor_free /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cpp:127
#1 0x557cbe82af60 in cache_tree_free /home/phil/src/git/cache-tree.c:35
#2 0x557cbe82aee5 in cache_tree_free /home/phil/src/git/cache-tree.c:31
#3 0x557cbe82aee5 in cache_tree_free /home/phil/src/git/cache-tree.c:31
#4 0x557cbe82aee5 in cache_tree_free /home/phil/src/git/cache-tree.c:31
#5 0x557cbeb2557a in ensure_full_index /home/phil/src/git/sparse-index.c:310
#6 0x557cbea45c4a in index_name_stage_pos /home/phil/src/git/read-cache.c:588
#7 0x557cbe82ce37 in verify_one /home/phil/src/git/cache-tree.c:850
#8 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#9 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#10 0x557cbe82ca9d in verify_one /home/phil/src/git/cache-tree.c:840
#11 0x557cbe830a2b in cache_tree_verify /home/phil/src/git/cache-tree.c:910
#12 0x557cbea53741 in write_locked_index /home/phil/src/git/read-cache.c:3250
#13 0x557cbeab7fdd in reset_head /home/phil/src/git/reset.c:87
#14 0x557cbe72147f in cmd_rebase builtin/rebase.c:2074
#15 0x557cbe5bd151 in run_builtin /home/phil/src/git/git.c:461
#16 0x557cbe5bd151 in handle_builtin /home/phil/src/git/git.c:714
#17 0x557cbe5c0503 in run_argv /home/phil/src/git/git.c:781
#18 0x557cbe5c0503 in cmd_main /home/phil/src/git/git.c:912
#19 0x557cbe5bad28 in main /home/phil/src/git/common-main.c:52
#20 0x7fdd4b82eb24 in __libc_start_main (/usr/lib/libc.so.6+0x27b24)
previously allocated by thread T0 here:
#0 0x7fdd4bad0459 in __interceptor_calloc /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cpp:154
#1 0x557cbebc1807 in xcalloc /home/phil/src/git/wrapper.c:140
#2 0x557cbe82b7d8 in cache_tree /home/phil/src/git/cache-tree.c:17
#3 0x557cbe82b7d8 in prime_cache_tree_rec /home/phil/src/git/cache-tree.c:763
#4 0x557cbe82b837 in prime_cache_tree_rec /home/phil/src/git/cache-tree.c:764
#5 0x557cbe82b837 in prime_cache_tree_rec /home/phil/src/git/cache-tree.c:764
#6 0x557cbe8304e1 in prime_cache_tree /home/phil/src/git/cache-tree.c:779
#7 0x557cbeab7fa7 in reset_head /home/phil/src/git/reset.c:85
#8 0x557cbe72147f in cmd_rebase builtin/rebase.c:2074
#9 0x557cbe5bd151 in run_builtin /home/phil/src/git/git.c:461
#10 0x557cbe5bd151 in handle_builtin /home/phil/src/git/git.c:714
#11 0x557cbe5c0503 in run_argv /home/phil/src/git/git.c:781
#12 0x557cbe5c0503 in cmd_main /home/phil/src/git/git.c:912
#13 0x557cbe5bad28 in main /home/phil/src/git/common-main.c:52
#14 0x7fdd4b82eb24 in __libc_start_main (/usr/lib/libc.so.6+0x27b24)
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
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). 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