Fix removing lazy initialization of repository state #15
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The commit that created the bug: 73f192c Lazy initialization was removed incorrectly!
remittor
force-pushed
the
fix_lazy_init
branch
from
5cc23bb to
9179811
Compare
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
There is an out-of-bounds read possible when parsing gitattributes that
have an attribute that is 2^31+1 bytes long. This is caused due to an
integer overflow when we assign the result of strlen(3P) to an `int`,
where we use the wrapped-around value in a subsequent call to
memcpy(3P). The following code reproduces the issue:
blob=$(perl -e 'print "a" x 2147483649 . " attr"' | git hash-object -w --stdin)
git update-index --add --cacheinfo 100644,$blob,.gitattributes
git check-attr --all file
AddressSanitizer:DEADLYSIGNAL
=================================================================
==8451==ERROR: AddressSanitizer: SEGV on unknown address 0x7f93efa00800 (pc 0x7f94f1f8f082 bp 0x7ffddb59b3a0 sp 0x7ffddb59ab28 T0)
==8451==The signal is caused by a READ memory access.
#0 0x7f94f1f8f082 (/usr/lib/libc.so.6+0x176082)
#1 0x7f94f2047d9c in __interceptor_strspn /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:752
#2 0x560e190f7f26 in parse_attr_line attr.c:375
#3 0x560e190f9663 in handle_attr_line attr.c:660
#4 0x560e190f9ddd in read_attr_from_index attr.c:769
#5 0x560e190f9f14 in read_attr attr.c:797
#6 0x560e190fa24e in bootstrap_attr_stack attr.c:867
#7 0x560e190fa4a5 in prepare_attr_stack attr.c:902
#8 0x560e190fb5dc in collect_some_attrs attr.c:1097
#9 0x560e190fb93f in git_all_attrs attr.c:1128
#10 0x560e18e6136e in check_attr builtin/check-attr.c:67
#11 0x560e18e61c12 in cmd_check_attr builtin/check-attr.c:183
#12 0x560e18e15993 in run_builtin git.c:466
#13 0x560e18e16397 in handle_builtin git.c:721
#14 0x560e18e16b2b in run_argv git.c:788
#15 0x560e18e17991 in cmd_main git.c:926
git#16 0x560e190ae2bd in main common-main.c:57
git#17 0x7f94f1e3c28f (/usr/lib/libc.so.6+0x2328f)
git#18 0x7f94f1e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#19 0x560e18e110e4 in _start ../sysdeps/x86_64/start.S:115
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/usr/lib/libc.so.6+0x176082)
==8451==ABORTING
Fix this bug by converting the variable to a `size_t` instead.
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
It is possible to trigger an integer overflow when parsing attribute
names when there are more than 2^31 of them for a single pattern. This
can either lead to us dying due to trying to request too many bytes:
blob=$(perl -e 'print "f" . " a=" x 2147483649' | git hash-object -w --stdin)
git update-index --add --cacheinfo 100644,$blob,.gitattributes
git attr-check --all file
=================================================================
==1022==ERROR: AddressSanitizer: requested allocation size 0xfffffff800000032 (0xfffffff800001038 after adjustments for alignment, red zones etc.) exceeds maximum supported size of 0x10000000000 (thread T0)
#0 0x7fd3efabf411 in __interceptor_calloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:77
#1 0x5563a0a1e3d3 in xcalloc wrapper.c:150
#2 0x5563a058d005 in parse_attr_line attr.c:384
#3 0x5563a058e661 in handle_attr_line attr.c:660
#4 0x5563a058eddb in read_attr_from_index attr.c:769
#5 0x5563a058ef12 in read_attr attr.c:797
#6 0x5563a058f24c in bootstrap_attr_stack attr.c:867
#7 0x5563a058f4a3 in prepare_attr_stack attr.c:902
#8 0x5563a05905da in collect_some_attrs attr.c:1097
#9 0x5563a059093d in git_all_attrs attr.c:1128
#10 0x5563a02f636e in check_attr builtin/check-attr.c:67
#11 0x5563a02f6c12 in cmd_check_attr builtin/check-attr.c:183
#12 0x5563a02aa993 in run_builtin git.c:466
#13 0x5563a02ab397 in handle_builtin git.c:721
#14 0x5563a02abb2b in run_argv git.c:788
#15 0x5563a02ac991 in cmd_main git.c:926
git#16 0x5563a05432bd in main common-main.c:57
git#17 0x7fd3ef82228f (/usr/lib/libc.so.6+0x2328f)
==1022==HINT: if you don't care about these errors you may set allocator_may_return_null=1
SUMMARY: AddressSanitizer: allocation-size-too-big /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:77 in __interceptor_calloc
==1022==ABORTING
Or, much worse, it can lead to an out-of-bounds write because we
underallocate and then memcpy(3P) into an array:
perl -e '
print "A " . "\rh="x2000000000;
print "\rh="x2000000000;
print "\rh="x294967294 . "\n"
' >.gitattributes
git add .gitattributes
git commit -am "evil attributes"
$ git clone --quiet /path/to/repo
=================================================================
==15062==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000002550 at pc 0x5555559884d5 bp 0x7fffffffbc60 sp 0x7fffffffbc58
WRITE of size 8 at 0x602000002550 thread T0
#0 0x5555559884d4 in parse_attr_line attr.c:393
#1 0x5555559884d4 in handle_attr_line attr.c:660
#2 0x555555988902 in read_attr_from_index attr.c:784
#3 0x555555988902 in read_attr_from_index attr.c:747
#4 0x555555988a1d in read_attr attr.c:800
#5 0x555555989b0c in bootstrap_attr_stack attr.c:882
#6 0x555555989b0c in prepare_attr_stack attr.c:917
#7 0x555555989b0c in collect_some_attrs attr.c:1112
#8 0x55555598b141 in git_check_attr attr.c:1126
#9 0x555555a13004 in convert_attrs convert.c:1311
#10 0x555555a95e04 in checkout_entry_ca entry.c:553
#11 0x555555d58bf6 in checkout_entry entry.h:42
#12 0x555555d58bf6 in check_updates unpack-trees.c:480
#13 0x555555d5eb55 in unpack_trees unpack-trees.c:2040
#14 0x555555785ab7 in checkout builtin/clone.c:724
#15 0x555555785ab7 in cmd_clone builtin/clone.c:1384
git#16 0x55555572443c in run_builtin git.c:466
git#17 0x55555572443c in handle_builtin git.c:721
git#18 0x555555727872 in run_argv git.c:788
git#19 0x555555727872 in cmd_main git.c:926
git#20 0x555555721fa0 in main common-main.c:57
git#21 0x7ffff73f1d09 in __libc_start_main ../csu/libc-start.c:308
git#22 0x555555723f39 in _start (git+0x1cff39)
0x602000002552 is located 0 bytes to the right of 2-byte region [0x602000002550,0x602000002552) allocated by thread T0 here:
#0 0x7ffff768c037 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
#1 0x555555d7fff7 in xcalloc wrapper.c:150
#2 0x55555598815f in parse_attr_line attr.c:384
#3 0x55555598815f in handle_attr_line attr.c:660
#4 0x555555988902 in read_attr_from_index attr.c:784
#5 0x555555988902 in read_attr_from_index attr.c:747
#6 0x555555988a1d in read_attr attr.c:800
#7 0x555555989b0c in bootstrap_attr_stack attr.c:882
#8 0x555555989b0c in prepare_attr_stack attr.c:917
#9 0x555555989b0c in collect_some_attrs attr.c:1112
#10 0x55555598b141 in git_check_attr attr.c:1126
#11 0x555555a13004 in convert_attrs convert.c:1311
#12 0x555555a95e04 in checkout_entry_ca entry.c:553
#13 0x555555d58bf6 in checkout_entry entry.h:42
#14 0x555555d58bf6 in check_updates unpack-trees.c:480
#15 0x555555d5eb55 in unpack_trees unpack-trees.c:2040
git#16 0x555555785ab7 in checkout builtin/clone.c:724
git#17 0x555555785ab7 in cmd_clone builtin/clone.c:1384
git#18 0x55555572443c in run_builtin git.c:466
git#19 0x55555572443c in handle_builtin git.c:721
git#20 0x555555727872 in run_argv git.c:788
git#21 0x555555727872 in cmd_main git.c:926
git#22 0x555555721fa0 in main common-main.c:57
git#23 0x7ffff73f1d09 in __libc_start_main ../csu/libc-start.c:308
SUMMARY: AddressSanitizer: heap-buffer-overflow attr.c:393 in parse_attr_line
Shadow bytes around the buggy address:
0x0c047fff8450: fa fa 00 02 fa fa 00 07 fa fa fd fd fa fa 00 00
0x0c047fff8460: fa fa 02 fa fa fa fd fd fa fa 00 06 fa fa 05 fa
0x0c047fff8470: fa fa fd fd fa fa 00 02 fa fa 06 fa fa fa 05 fa
0x0c047fff8480: fa fa 07 fa fa fa fd fd fa fa 00 01 fa fa 00 02
0x0c047fff8490: fa fa 00 03 fa fa 00 fa fa fa 00 01 fa fa 00 03
=>0x0c047fff84a0: fa fa 00 01 fa fa 00 02 fa fa[02]fa fa fa fa fa
0x0c047fff84b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff84c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff84d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff84e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff84f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==15062==ABORTING
Fix this bug by using `size_t` instead to count the number of attributes
so that this value cannot reasonably overflow without running out of
memory before already.
Reported-by: Markus Vervier <[email protected]>
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
When using a padding specifier in the pretty format passed to git-log(1)
we need to calculate the string length in several places. These string
lengths are stored in `int`s though, which means that these can easily
overflow when the input lengths exceeds 2GB. This can ultimately lead to
an out-of-bounds write when these are used in a call to memcpy(3P):
==8340==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f1ec62f97fe at pc 0x7f2127e5f427 bp 0x7ffd3bd63de0 sp 0x7ffd3bd63588
WRITE of size 1 at 0x7f1ec62f97fe thread T0
#0 0x7f2127e5f426 in __interceptor_memcpy /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827
#1 0x5628e96aa605 in format_and_pad_commit pretty.c:1762
#2 0x5628e96aa7f4 in format_commit_item pretty.c:1801
#3 0x5628e97cdb24 in strbuf_expand strbuf.c:429
#4 0x5628e96ab060 in repo_format_commit_message pretty.c:1869
#5 0x5628e96acd0f in pretty_print_commit pretty.c:2161
#6 0x5628e95a44c8 in show_log log-tree.c:781
#7 0x5628e95a76ba in log_tree_commit log-tree.c:1117
#8 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508
#9 0x5628e922c35b in cmd_log_walk builtin/log.c:549
#10 0x5628e922f1a2 in cmd_log builtin/log.c:883
#11 0x5628e9106993 in run_builtin git.c:466
#12 0x5628e9107397 in handle_builtin git.c:721
#13 0x5628e9107b07 in run_argv git.c:788
#14 0x5628e91088a7 in cmd_main git.c:923
#15 0x5628e939d682 in main common-main.c:57
git#16 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f)
git#17 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#18 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115
0x7f1ec62f97fe is located 2 bytes to the left of 4831838265-byte region [0x7f1ec62f9800,0x7f1fe62f9839)
allocated by thread T0 here:
#0 0x7f2127ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85
#1 0x5628e98774d4 in xrealloc wrapper.c:136
#2 0x5628e97cb01c in strbuf_grow strbuf.c:99
#3 0x5628e97ccd42 in strbuf_addchars strbuf.c:327
#4 0x5628e96aa55c in format_and_pad_commit pretty.c:1761
#5 0x5628e96aa7f4 in format_commit_item pretty.c:1801
#6 0x5628e97cdb24 in strbuf_expand strbuf.c:429
#7 0x5628e96ab060 in repo_format_commit_message pretty.c:1869
#8 0x5628e96acd0f in pretty_print_commit pretty.c:2161
#9 0x5628e95a44c8 in show_log log-tree.c:781
#10 0x5628e95a76ba in log_tree_commit log-tree.c:1117
#11 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508
#12 0x5628e922c35b in cmd_log_walk builtin/log.c:549
#13 0x5628e922f1a2 in cmd_log builtin/log.c:883
#14 0x5628e9106993 in run_builtin git.c:466
#15 0x5628e9107397 in handle_builtin git.c:721
git#16 0x5628e9107b07 in run_argv git.c:788
git#17 0x5628e91088a7 in cmd_main git.c:923
git#18 0x5628e939d682 in main common-main.c:57
git#19 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f)
git#20 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#21 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115
SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 in __interceptor_memcpy
Shadow bytes around the buggy address:
0x0fe458c572a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0fe458c572b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0fe458c572c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0fe458c572d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0fe458c572e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0fe458c572f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa]
0x0fe458c57300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe458c57310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe458c57320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe458c57330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe458c57340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==8340==ABORTING
The pretty format can also be used in `git archive` operations via the
`export-subst` attribute. So this is what in our opinion makes this a
critical issue in the context of Git forges which allow to download an
archive of user supplied Git repositories.
Fix this vulnerability by using `size_t` instead of `int` to track the
string lengths. Add tests which detect this vulnerability when Git is
compiled with the address sanitizer.
Reported-by: Joern Schneeweisz <[email protected]>
Original-patch-by: Joern Schneeweisz <[email protected]>
Modified-by: Taylor Blau <[email protected]>
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
With the `%>>(<N>)` pretty formatter, you can ask git-log(1) et al to
steal spaces. To do so we need to look ahead of the next token to see
whether there are spaces there. This loop takes into account ANSI
sequences that end with an `m`, and if it finds any it will skip them
until it finds the first space. While doing so it does not take into
account the buffer's limits though and easily does an out-of-bounds
read.
Add a test that hits this behaviour. While we don't have an easy way to
verify this, the test causes the following failure when run with
`SANITIZE=address`:
==37941==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000000baf at pc 0x55ba6f88e0d0 bp 0x7ffc84c50d20 sp 0x7ffc84c50d10
READ of size 1 at 0x603000000baf thread T0
#0 0x55ba6f88e0cf in format_and_pad_commit pretty.c:1712
#1 0x55ba6f88e7b4 in format_commit_item pretty.c:1801
#2 0x55ba6f9b1ae4 in strbuf_expand strbuf.c:429
#3 0x55ba6f88f020 in repo_format_commit_message pretty.c:1869
#4 0x55ba6f890ccf in pretty_print_commit pretty.c:2161
#5 0x55ba6f7884c8 in show_log log-tree.c:781
#6 0x55ba6f78b6ba in log_tree_commit log-tree.c:1117
#7 0x55ba6f40fed5 in cmd_log_walk_no_free builtin/log.c:508
#8 0x55ba6f41035b in cmd_log_walk builtin/log.c:549
#9 0x55ba6f4131a2 in cmd_log builtin/log.c:883
#10 0x55ba6f2ea993 in run_builtin git.c:466
#11 0x55ba6f2eb397 in handle_builtin git.c:721
#12 0x55ba6f2ebb07 in run_argv git.c:788
#13 0x55ba6f2ec8a7 in cmd_main git.c:923
#14 0x55ba6f581682 in main common-main.c:57
#15 0x7f2d08c3c28f (/usr/lib/libc.so.6+0x2328f)
git#16 0x7f2d08c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#17 0x55ba6f2e60e4 in _start ../sysdeps/x86_64/start.S:115
0x603000000baf is located 1 bytes to the left of 24-byte region [0x603000000bb0,0x603000000bc8)
allocated by thread T0 here:
#0 0x7f2d08ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85
#1 0x55ba6fa5b494 in xrealloc wrapper.c:136
#2 0x55ba6f9aefdc in strbuf_grow strbuf.c:99
#3 0x55ba6f9b0a06 in strbuf_add strbuf.c:298
#4 0x55ba6f9b1a25 in strbuf_expand strbuf.c:418
#5 0x55ba6f88f020 in repo_format_commit_message pretty.c:1869
#6 0x55ba6f890ccf in pretty_print_commit pretty.c:2161
#7 0x55ba6f7884c8 in show_log log-tree.c:781
#8 0x55ba6f78b6ba in log_tree_commit log-tree.c:1117
#9 0x55ba6f40fed5 in cmd_log_walk_no_free builtin/log.c:508
#10 0x55ba6f41035b in cmd_log_walk builtin/log.c:549
#11 0x55ba6f4131a2 in cmd_log builtin/log.c:883
#12 0x55ba6f2ea993 in run_builtin git.c:466
#13 0x55ba6f2eb397 in handle_builtin git.c:721
#14 0x55ba6f2ebb07 in run_argv git.c:788
#15 0x55ba6f2ec8a7 in cmd_main git.c:923
git#16 0x55ba6f581682 in main common-main.c:57
git#17 0x7f2d08c3c28f (/usr/lib/libc.so.6+0x2328f)
git#18 0x7f2d08c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#19 0x55ba6f2e60e4 in _start ../sysdeps/x86_64/start.S:115
SUMMARY: AddressSanitizer: heap-buffer-overflow pretty.c:1712 in format_and_pad_commit
Shadow bytes around the buggy address:
0x0c067fff8120: fa fa fd fd fd fa fa fa fd fd fd fa fa fa fd fd
0x0c067fff8130: fd fd fa fa fd fd fd fd fa fa fd fd fd fa fa fa
0x0c067fff8140: fd fd fd fa fa fa fd fd fd fa fa fa fd fd fd fa
0x0c067fff8150: fa fa fd fd fd fd fa fa 00 00 00 fa fa fa fd fd
0x0c067fff8160: fd fa fa fa fd fd fd fa fa fa fd fd fd fa fa fa
=>0x0c067fff8170: fd fd fd fa fa[fa]00 00 00 fa fa fa 00 00 00 fa
0x0c067fff8180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff8190: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff81a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff81b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff81c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Luckily enough, this would only cause us to copy the out-of-bounds data
into the formatted commit in case we really had an ANSI sequence
preceding our buffer. So this bug likely has no security consequences.
Fix it regardless by not traversing past the buffer's start.
Reported-by: Patrick Steinhardt <[email protected]>
Reported-by: Eric Sesterhenn <[email protected]>
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
An out-of-bounds read can be triggered when parsing an incomplete padding format string passed via `--pretty=format` or in Git archives when files are marked with the `export-subst` gitattribute. This bug exists since we have introduced support for truncating output via the `trunc` keyword a7f01c6 (pretty: support truncating in %>, %< and %><, 2013-04-19). Before this commit, we used to find the end of the formatting string by using strchr(3P). This function returns a `NULL` pointer in case the character in question wasn't found. The subsequent check whether any character was found thus simply checked the returned pointer. After the commit we switched to strcspn(3P) though, which only returns the offset to the first found character or to the trailing NUL byte. As the end pointer is now computed by adding the offset to the start pointer it won't be `NULL` anymore, and as a consequence the check doesn't do anything anymore. The out-of-bounds data that is being read can in fact end up in the formatted string. As a consequence, it is possible to leak memory contents either by calling git-log(1) or via git-archive(1) when any of the archived files is marked with the `export-subst` gitattribute. ==10888==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000398 at pc 0x7f0356047cb2 bp 0x7fff3ffb95d0 sp 0x7fff3ffb8d78 READ of size 1 at 0x602000000398 thread T0 #0 0x7f0356047cb1 in __interceptor_strchrnul /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:725 #1 0x563b7cec9a43 in strbuf_expand strbuf.c:417 #2 0x563b7cda7060 in repo_format_commit_message pretty.c:1869 #3 0x563b7cda8d0f in pretty_print_commit pretty.c:2161 #4 0x563b7cca04c8 in show_log log-tree.c:781 #5 0x563b7cca36ba in log_tree_commit log-tree.c:1117 #6 0x563b7c927ed5 in cmd_log_walk_no_free builtin/log.c:508 #7 0x563b7c92835b in cmd_log_walk builtin/log.c:549 #8 0x563b7c92b1a2 in cmd_log builtin/log.c:883 #9 0x563b7c802993 in run_builtin git.c:466 #10 0x563b7c803397 in handle_builtin git.c:721 #11 0x563b7c803b07 in run_argv git.c:788 #12 0x563b7c8048a7 in cmd_main git.c:923 #13 0x563b7ca99682 in main common-main.c:57 #14 0x7f0355e3c28f (/usr/lib/libc.so.6+0x2328f) #15 0x7f0355e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) git#16 0x563b7c7fe0e4 in _start ../sysdeps/x86_64/start.S:115 0x602000000398 is located 0 bytes to the right of 8-byte region [0x602000000390,0x602000000398) allocated by thread T0 here: #0 0x7f0356072faa in __interceptor_strdup /usr/src/debug/gcc/libsanitizer/asan/asan_interceptors.cpp:439 #1 0x563b7cf7317c in xstrdup wrapper.c:39 #2 0x563b7cd9a06a in save_user_format pretty.c:40 #3 0x563b7cd9b3e5 in get_commit_format pretty.c:173 #4 0x563b7ce54ea0 in handle_revision_opt revision.c:2456 #5 0x563b7ce597c9 in setup_revisions revision.c:2850 #6 0x563b7c9269e0 in cmd_log_init_finish builtin/log.c:269 #7 0x563b7c927362 in cmd_log_init builtin/log.c:348 #8 0x563b7c92b193 in cmd_log builtin/log.c:882 #9 0x563b7c802993 in run_builtin git.c:466 #10 0x563b7c803397 in handle_builtin git.c:721 #11 0x563b7c803b07 in run_argv git.c:788 #12 0x563b7c8048a7 in cmd_main git.c:923 #13 0x563b7ca99682 in main common-main.c:57 #14 0x7f0355e3c28f (/usr/lib/libc.so.6+0x2328f) #15 0x7f0355e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) git#16 0x563b7c7fe0e4 in _start ../sysdeps/x86_64/start.S:115 SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:725 in __interceptor_strchrnul Shadow bytes around the buggy address: 0x0c047fff8020: fa fa fd fd fa fa 00 06 fa fa 05 fa fa fa fd fd 0x0c047fff8030: fa fa 00 02 fa fa 06 fa fa fa 05 fa fa fa fd fd 0x0c047fff8040: fa fa 00 07 fa fa 03 fa fa fa fd fd fa fa 00 00 0x0c047fff8050: fa fa 00 01 fa fa fd fd fa fa 00 00 fa fa 00 01 0x0c047fff8060: fa fa 00 06 fa fa 00 06 fa fa 05 fa fa fa 05 fa =>0x0c047fff8070: fa fa 00[fa]fa fa fd fa fa fa fd fd fa fa fd fd 0x0c047fff8080: fa fa fd fd fa fa 00 00 fa fa 00 fa fa fa fd fa 0x0c047fff8090: fa fa fd fd fa fa 00 00 fa fa fa fa fa fa fa fa 0x0c047fff80a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c047fff80b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c047fff80c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==10888==ABORTING Fix this bug by checking whether `end` points at the trailing NUL byte. Add a test which catches this out-of-bounds read and which demonstrates that we used to write out-of-bounds data into the formatted message. Reported-by: Markus Vervier <[email protected]> Original-patch-by: Markus Vervier <[email protected]> Signed-off-by: Patrick Steinhardt <[email protected]> Signed-off-by: Junio C Hamano <[email protected]>
csware
pushed a commit
that referenced
this pull request
Jan 19, 2023
The return type of both `utf8_strwidth()` and `utf8_strnwidth()` is
`int`, but we operate on string lengths which are typically of type
`size_t`. This means that when the string is longer than `INT_MAX`, we
will overflow and thus return a negative result.
This can lead to an out-of-bounds write with `--pretty=format:%<1)%B`
and a commit message that is 2^31+1 bytes long:
=================================================================
==26009==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000001168 at pc 0x7f95c4e5f427 bp 0x7ffd8541c900 sp 0x7ffd8541c0a8
WRITE of size 2147483649 at 0x603000001168 thread T0
#0 0x7f95c4e5f426 in __interceptor_memcpy /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827
#1 0x5612bbb1068c in format_and_pad_commit pretty.c:1763
#2 0x5612bbb1087a in format_commit_item pretty.c:1801
#3 0x5612bbc33bab in strbuf_expand strbuf.c:429
#4 0x5612bbb110e7 in repo_format_commit_message pretty.c:1869
#5 0x5612bbb12d96 in pretty_print_commit pretty.c:2161
#6 0x5612bba0a4d5 in show_log log-tree.c:781
#7 0x5612bba0d6c7 in log_tree_commit log-tree.c:1117
#8 0x5612bb691ed5 in cmd_log_walk_no_free builtin/log.c:508
#9 0x5612bb69235b in cmd_log_walk builtin/log.c:549
#10 0x5612bb6951a2 in cmd_log builtin/log.c:883
#11 0x5612bb56c993 in run_builtin git.c:466
#12 0x5612bb56d397 in handle_builtin git.c:721
#13 0x5612bb56db07 in run_argv git.c:788
#14 0x5612bb56e8a7 in cmd_main git.c:923
#15 0x5612bb803682 in main common-main.c:57
git#16 0x7f95c4c3c28f (/usr/lib/libc.so.6+0x2328f)
git#17 0x7f95c4c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349)
git#18 0x5612bb5680e4 in _start ../sysdeps/x86_64/start.S:115
0x603000001168 is located 0 bytes to the right of 24-byte region [0x603000001150,0x603000001168)
allocated by thread T0 here:
#0 0x7f95c4ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85
#1 0x5612bbcdd556 in xrealloc wrapper.c:136
#2 0x5612bbc310a3 in strbuf_grow strbuf.c:99
#3 0x5612bbc32acd in strbuf_add strbuf.c:298
#4 0x5612bbc33aec in strbuf_expand strbuf.c:418
#5 0x5612bbb110e7 in repo_format_commit_message pretty.c:1869
#6 0x5612bbb12d96 in pretty_print_commit pretty.c:2161
#7 0x5612bba0a4d5 in show_log log-tree.c:781
#8 0x5612bba0d6c7 in log_tree_commit log-tree.c:1117
#9 0x5612bb691ed5 in cmd_log_walk_no_free builtin/log.c:508
#10 0x5612bb69235b in cmd_log_walk builtin/log.c:549
#11 0x5612bb6951a2 in cmd_log builtin/log.c:883
#12 0x5612bb56c993 in run_builtin git.c:466
#13 0x5612bb56d397 in handle_builtin git.c:721
#14 0x5612bb56db07 in run_argv git.c:788
#15 0x5612bb56e8a7 in cmd_main git.c:923
git#16 0x5612bb803682 in main common-main.c:57
git#17 0x7f95c4c3c28f (/usr/lib/libc.so.6+0x2328f)
SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 in __interceptor_memcpy
Shadow bytes around the buggy address:
0x0c067fff81d0: fd fd fd fa fa fa fd fd fd fa fa fa fd fd fd fa
0x0c067fff81e0: fa fa fd fd fd fd fa fa fd fd fd fd fa fa fd fd
0x0c067fff81f0: fd fa fa fa fd fd fd fa fa fa fd fd fd fa fa fa
0x0c067fff8200: fd fd fd fa fa fa fd fd fd fd fa fa 00 00 00 fa
0x0c067fff8210: fa fa fd fd fd fa fa fa fd fd fd fa fa fa fd fd
=>0x0c067fff8220: fd fa fa fa fd fd fd fa fa fa 00 00 00[fa]fa fa
0x0c067fff8230: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff8240: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff8250: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff8260: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c067fff8270: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==26009==ABORTING
Now the proper fix for this would be to convert both functions to return
an `size_t` instead of an `int`. But given that this commit may be part
of a security release, let's instead do the minimal viable fix and die
in case we see an overflow.
Add a test that would have previously caused us to crash.
Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit is the cause of the error: 73f192c
Lazy initialization was removed incorrectly!
After these changes, the dependent code began to work incorrectly:
https://github.com/TortoiseGit/TortoiseGit/blob/364ebc6e686828b24964845bdb52445b645b9e27/ext/gitdll/gitdll.c#L888-L890