Return-Path: MIME-Version: 1.0 In-Reply-To: <1457384483-19894-1-git-send-email-dev@codyps.com> References: <1457384483-19894-1-git-send-email-dev@codyps.com> Date: Wed, 9 Mar 2016 12:50:19 +0200 Message-ID: Subject: Re: [PATCH BlueZ] uuid: fix 1 byte stack overflow From: Luiz Augusto von Dentz To: Cody P Schafer Cc: "linux-bluetooth@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Cody, On Mon, Mar 7, 2016 at 11:01 PM, Cody P Schafer 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