Alice C. Munduruca wrote:
> When the selftest 'tap.c' is compiled with '-D_FORTIFY_SOURCE=3', the
> strcpy() in rtattr_add_strsz() is replaced with a checked version which
> causes the test to consistently fail when compiled with toolchains for
> which this option is enabled by default.
>
> TAP version 13
> 1..3
> # Starting 3 tests from 1 test cases.
> # RUN tap.test_packet_valid_udp_gso ...
> *** buffer overflow detected ***: terminated
> # test_packet_valid_udp_gso: Test terminated by assertion
> # FAIL tap.test_packet_valid_udp_gso
> not ok 1 tap.test_packet_valid_udp_gso
> # RUN tap.test_packet_valid_udp_csum ...
> *** buffer overflow detected ***: terminated
> # test_packet_valid_udp_csum: Test terminated by assertion
> # FAIL tap.test_packet_valid_udp_csum
> not ok 2 tap.test_packet_valid_udp_csum
> # RUN tap.test_packet_crash_tap_invalid_eth_proto ...
> *** buffer overflow detected ***: terminated
> # test_packet_crash_tap_invalid_eth_proto: Test terminated by assertion
> # FAIL tap.test_packet_crash_tap_invalid_eth_proto
> not ok 3 tap.test_packet_crash_tap_invalid_eth_proto
> # FAILED: 0 / 3 tests passed.
> # Totals: pass:0 fail:3 xfail:0 xpass:0 skip:0 error:0
>
> A buffer overflow is detected by the fortified glibc __strcpy_chk()
> since the __builtin_object_size() of `RTA_DATA(rta)` is incorrectly
> reported as 1, even though there is ample space in its bounding buffer
> `req`.
>
> Using the unchecked function memcpy() here instead allows us to match
> the way rtattr_add_str() is written while avoiding the spurious test
> failure.
>
> Fixes: 2e64fe4624d1 ("selftests: add few test cases for tap driver")
> Signed-off-by: Alice C. Munduruca <[email protected]>
> ---
> tools/testing/selftests/net/tap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/net/tap.c
> b/tools/testing/selftests/net/tap.c
> index 247c3b3ac1c9..dd961b629295 100644
> --- a/tools/testing/selftests/net/tap.c
> +++ b/tools/testing/selftests/net/tap.c
> @@ -67,7 +67,7 @@ static struct rtattr *rtattr_add_strsz(struct nlmsghdr *nh,
> unsigned short type,
> {
> struct rtattr *rta = rtattr_add(nh, type, strlen(s) + 1);
>
> - strcpy(RTA_DATA(rta), s);
> + memcpy(RTA_DATA(rta), s, strlen(s) + 1);
Could call strlen(s) only once in the function.
Why does rtattr_add_str do the same without the terminating '\0'?
It is only used with IFNAME so assumes max size of IFNAMSIZ perhaps?
> return rta;
> }
>
> --
> 2.48.1
>
