net:tap in ubuntu_kselftests_net fails on Noble

[Kevin Becker]

The following issue has been found in net:tap in ubuntu_kselftests_net on multiple noble kernels (including generic, realtime, and ibm):

 8819 14:42:24 DEBUG| [stdout] TAP version 13
 8820 14:42:24 DEBUG| [stdout] 1..1
 8821 14:42:24 DEBUG| [stdout] # timeout set to 0
 8822 14:42:24 DEBUG| [stdout] # selftests: net: tap
 8823 14:42:24 DEBUG| [stdout] # TAP version 13
 8824 14:42:24 DEBUG| [stdout] # 1..3
 8825 14:42:24 DEBUG| [stdout] # # Starting 3 tests from 1 test cases.
 8826 14:42:24 DEBUG| [stdout] # # RUN tap.test_packet_valid_udp_gso ...
 8827 14:42:24 DEBUG| [stdout] # *** buffer overflow detected ***: terminated
 8828 14:42:24 DEBUG| [stdout] # # test_packet_valid_udp_gso: Test terminated by assertion
 8829 14:42:24 DEBUG| [stdout] # # FAIL tap.test_packet_valid_udp_gso
 8830 14:42:24 DEBUG| [stdout] # not ok 1 tap.test_packet_valid_udp_gso
 8831 14:42:24 DEBUG| [stdout] # # RUN tap.test_packet_valid_udp_csum ...
 8832 14:42:24 DEBUG| [stdout] # *** buffer overflow detected ***: terminated
 8833 14:42:25 DEBUG| [stdout] # # test_packet_valid_udp_csum: Test terminated by assertion
 8834 14:42:25 DEBUG| [stdout] # # FAIL tap.test_packet_valid_udp_csum
 8835 14:42:25 DEBUG| [stdout] # not ok 2 tap.test_packet_valid_udp_csum
 8836 14:42:25 DEBUG| [stdout] # # RUN tap.test_packet_crash_tap_invalid_eth_proto ...
 8837 14:42:25 DEBUG| [stdout] # *** buffer overflow detected ***: terminated
 8838 14:42:25 DEBUG| [stdout] # # test_packet_crash_tap_invalid_eth_proto: Test terminated by assertion
 8839 14:42:25 DEBUG| [stdout] # # FAIL tap.test_packet_crash_tap_invalid_eth_proto
 8840 14:42:25 DEBUG| [stdout] # not ok 3 tap.test_packet_crash_tap_invalid_eth_proto
 8841 14:42:25 DEBUG| [stdout] # # FAILED: 0 / 3 tests passed.
 8842 14:42:25 DEBUG| [stdout] # # Totals: pass:0 fail:3 xfail:0 xpass:0 skip:0 error:0

[Magali Lemes do Sacramento (magalilemes)]

This seems to have emerged with the addition of -D_FORTIFY_SOURCE=3 to the default build flags of gcc in 24.04.
With that flag set, a buffer overflow is detected at strcpy[1], which could (seems to) be a false positive. Unsure if a proper fix would be changing that to memcpy or even understanding gcc's assumptions here 😀

[1]: https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/noble/tree/tools/testing/selftests/net/tap.c?h=Ubuntu-6.8.0-38.38#n70