On 17 May 2024, at 20:33, Ilya Maximets wrote:
> Segments list in SRv6 header is 16-bit aligned as most of other fields
> in packet headers. A little counter-intuitively, compilers are allowed
> to make alignment assumptions based on the pointer type passed to
> memcpy(), so they can use copy instructions that require 32-bit alignment
> in case of struct in6_addr pointer. Reported by UBsan in Clang 18:
>
> lib/netdev-native-tnl.c:985:16: runtime error: store to misaligned
> address 0x7fd9e97351ce for type 'struct in6_addr *', which
> requires 4 byte alignment
> 0x7fd9e97351ce: note: pointer points here
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ^
> 0 0xc1de38 in netdev_srv6_build_header lib/netdev-native-tnl.c:985:9
> 1 0x6e794b in tnl_port_build_header ofproto/tunnel.c:751:11
> 2 0x6c9c0a in native_tunnel_output ofproto/ofproto-dpif-xlate.c:3887:11
> 3 0x6c9c0a in compose_output_action__ ofproto/ofproto-dpif-xlate.c:4502:13
> 4 0x6b6646 in compose_output_action ofproto/ofproto-dpif-xlate.c:4564:5
> 5 0x6b6646 in xlate_output_action ofproto/ofproto-dpif-xlate.c:5517:13
> 6 0x68cfee in do_xlate_actions ofproto/ofproto-dpif-xlate.c:7288:13
> 7 0x67fed0 in xlate_actions ofproto/ofproto-dpif-xlate.c:8314:13
> 8 0x6468bd in ofproto_trace__ ofproto/ofproto-dpif-trace.c:782:30
> 9 0x64484a in ofproto_trace ofproto/ofproto-dpif-trace.c:851:5
> 10 0x647469 in ofproto_unixctl_trace ofproto/ofproto-dpif-trace.c:490:9
> 11 0xc33771 in process_command lib/unixctl.c:310:13
> 12 0xc33771 in run_connection lib/unixctl.c:344:17
> 13 0xc33771 in unixctl_server_run lib/unixctl.c:395:21
> 14 0x53e6ef in main vswitchd/ovs-vswitchd.c:131:9
> 15 0x7f61c7 in __libc_start_call_main (/lib64/libc.so.6+0x2a1c7)
> 16 0x7f628a in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x2a28a)
> 17 0x42ca24 in _start (vswitchd/ovs-vswitchd+0x42ca24)
>
> SUMMARY: UndefinedBehaviorSanitizer:
> undefined-behavior lib/netdev-native-tnl.c:985:16
>
> Having misaligned pointers is also generally not allowed in C, let
> alone accessing memory through them.
>
> Fix that by using an appropriate ovs_16aligned_in6_addr pointer instead.
>
> Fixes: 7381fd440a88 ("odp: Add SRv6 tunnel actions.")
> Fixes: 03fc1ad78521 ("userspace: Add SRv6 tunnel support.")
> Signed-off-by: Ilya Maximets <[email protected]>
Thanks for fixing this, looks good to me.
Acked-by: Eelco Chaudron <[email protected]>
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