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attr: fix out-of-bounds write when parsing huge number of attributes
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
#16 0x5563a05432bd in main common-main.c:57
#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
#16 0x55555572443c in run_builtin git.c:466
#17 0x55555572443c in handle_builtin git.c:721
#18 0x555555727872 in run_argv git.c:788
#19 0x555555727872 in cmd_main git.c:926
#20 0x555555721fa0 in main common-main.c:57
#21 0x7ffff73f1d09 in __libc_start_main ../csu/libc-start.c:308
#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
#16 0x555555785ab7 in checkout builtin/clone.c:724
#17 0x555555785ab7 in cmd_clone builtin/clone.c:1384
#18 0x55555572443c in run_builtin git.c:466
#19 0x55555572443c in handle_builtin git.c:721
#20 0x555555727872 in run_argv git.c:788
#21 0x555555727872 in cmd_main git.c:926
#22 0x555555721fa0 in main common-main.c:57
#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 <markus.vervier@x41-dsec.de>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Patrick Steinhardt
Junio C Hamano
parent
2455720950
commit
34ace8bad0
16
attr.c
16
attr.c
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@ -272,7 +272,7 @@ struct match_attr {
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const struct git_attr *attr;
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} u;
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char is_macro;
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unsigned num_attr;
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size_t num_attr;
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struct attr_state state[FLEX_ARRAY];
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};
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@ -333,8 +333,7 @@ static const char *parse_attr(const char *src, int lineno, const char *cp,
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static struct match_attr *parse_attr_line(const char *line, const char *src,
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int lineno, int macro_ok)
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{
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size_t namelen;
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int num_attr, i;
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size_t namelen, num_attr, i;
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const char *cp, *name, *states;
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struct match_attr *res = NULL;
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int is_macro;
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@ -451,7 +450,8 @@ static void attr_stack_free(struct attr_stack *e)
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free(e->origin);
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for (i = 0; i < e->num_matches; i++) {
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struct match_attr *a = e->attrs[i];
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int j;
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size_t j;
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for (j = 0; j < a->num_attr; j++) {
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const char *setto = a->state[j].setto;
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if (setto == ATTR__TRUE ||
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@ -1001,12 +1001,12 @@ static int macroexpand_one(struct all_attrs_item *all_attrs, int nr, int rem);
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static int fill_one(const char *what, struct all_attrs_item *all_attrs,
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const struct match_attr *a, int rem)
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{
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int i;
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size_t i;
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for (i = a->num_attr - 1; rem > 0 && i >= 0; i--) {
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const struct git_attr *attr = a->state[i].attr;
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for (i = a->num_attr; rem > 0 && i > 0; i--) {
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const struct git_attr *attr = a->state[i - 1].attr;
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const char **n = &(all_attrs[attr->attr_nr].value);
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const char *v = a->state[i].setto;
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const char *v = a->state[i - 1].setto;
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if (*n == ATTR__UNKNOWN) {
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debug_set(what,
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