Hi Cody,
On Mon, Mar 7, 2016 at 11:01 PM, Cody P Schafer <dev@xxxxxxxxxx> wrote:
> scanf requires that '[' convertion specifiers have enough room for all
> characters in the string, _plus a terminating null byte_. We were
> previously not providing room for the terminating null byte.
>
> This was detected by AddressSanitizer:
>
> ==15036==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffe4e774401 at pc 0x7fd33f572c98 bp 0x7ffe4e774270 sp 0x7ffe4e7739f8
> WRITE of size 2 at 0x7ffe4e774401 thread T0
> #0 0x7fd33f572c97 in scanf_common /build/gcc-multilib/src/gcc-5-20160209/libsanitizer/sanitizer_common/sanitizer_common_interceptors_format.inc:340
> #1 0x7fd33f5739ea in __interceptor_vsscanf /build/gcc-multilib/src/gcc-5-20160209/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:769
> #2 0x7fd33f573b49 in __interceptor_sscanf /build/gcc-multilib/src/gcc-5-20160209/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:793
> #3 0x650db5 in is_base_uuid128 lib/uuid.c:191
> #4 0x65196e in bt_string_to_uuid lib/uuid.c:267
> #5 0x56f28e in parse_uuid src/gatt-database.c:1473
> #6 0x5729e0 in database_add_service src/gatt-database.c:2053
> #7 0x57329f in database_add_app src/gatt-database.c:2106
> #8 0x573adc in client_ready_cb src/gatt-database.c:2211
> #9 0x6695fd in get_managed_objects_reply gdbus/client.c:1097
> #10 0x7fd33efd5391 (/usr/lib/libdbus-1.so.3+0x13391)
> #11 0x7fd33efd8db0 in dbus_connection_dispatch (/usr/lib/libdbus-1.so.3+0x16db0)
> #12 0x651ecd in message_dispatch gdbus/mainloop.c:72
> #13 0x7fd33f25cc39 in g_main_context_dispatch (/usr/lib/libglib-2.0.so.0+0x49c39)
> #14 0x7fd33f25cfdf (/usr/lib/libglib-2.0.so.0+0x49fdf)
> #15 0x7fd33f25d301 in g_main_loop_run (/usr/lib/libglib-2.0.so.0+0x4a301)
> #16 0x54b7d1 in main src/main.c:687
> #17 0x7fd33d90870f in __libc_start_main (/usr/lib/libc.so.6+0x2070f)
> #18 0x40bba8 in _start (/home/cody/g/bluez/src/bluetoothd+0x40bba8)
>
> Address 0x7ffe4e774401 is located in stack of thread T0 at offset 33 in frame
> #0 0x650ccd in is_base_uuid128 lib/uuid.c:184
>
> This frame has 2 object(s):
> [32, 33) 'dummy' <== Memory access at offset 33 overflows this variable
> [96, 98) 'uuid'
> HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
> (longjmp and C++ exceptions *are* supported)
> SUMMARY: AddressSanitizer: stack-buffer-overflow /build/gcc-multilib/src/gcc-5-20160209/libsanitizer/sanitizer_common/sanitizer_common_interceptors_format.inc:340 scanf_common
> Shadow bytes around the buggy address:
> 0x100049ce6830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x100049ce6840: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x100049ce6850: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x100049ce6860: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x100049ce6870: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
> =>0x100049ce6880:[01]f4 f4 f4 f2 f2 f2 f2 02 f4 f4 f4 f3 f3 f3 f3
> 0x100049ce6890: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
> 0x100049ce68a0: 00 f4 f4 f4 f2 f2 f2 f2 00 00 04 f4 f2 f2 f2 f2
> 0x100049ce68b0: 00 00 00 00 00 00 00 00 00 f4 f4 f4 f3 f3 f3 f3
> 0x100049ce68c0: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
> 0x100049ce68d0: 01 f4 f4 f4 f2 f2 f2 f2 00 00 04 f4 f3 f3 f3 f3
> 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
> Heap right redzone: fb
> Freed heap region: fd
> Stack left redzone: f1
> Stack mid redzone: f2
> Stack right redzone: f3
> Stack partial redzone: f4
> 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
> ==15036==ABORTING
> ---
> lib/uuid.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/uuid.c b/lib/uuid.c
> index 20b67d0..ac071fa 100644
> --- a/lib/uuid.c
> +++ b/lib/uuid.c
> @@ -183,14 +183,14 @@ static inline int is_uuid128(const char *string)
> static inline int is_base_uuid128(const char *string)
> {
> uint16_t uuid;
> - char dummy;
> + char dummy[2];
>
> if (!is_uuid128(string))
> return 0;
>
> return sscanf(string,
> "0000%04hx-0000-1000-8000-00805%1[fF]9%1[bB]34%1[fF]%1[bB]",
> - &uuid, &dummy, &dummy, &dummy, &dummy) == 5;
> + &uuid, dummy, dummy, dummy, dummy) == 5;
> }
>
> static inline int is_uuid32(const char *string)
> --
> 2.7.2
Applied, thanks.
--
Luiz Augusto von Dentz
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