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 <i.maxim...@ovn.org>
---
lib/netdev-native-tnl.c | 5 ++---
lib/odp-util.c | 4 ++--
2 files changed, 4 insertions(+), 5 deletions(-)
diff --git a/lib/netdev-native-tnl.c b/lib/netdev-native-tnl.c
index dee9ab344..b21176037 100644
--- a/lib/netdev-native-tnl.c
+++ b/lib/netdev-native-tnl.c
@@ -932,9 +932,9 @@ netdev_srv6_build_header(const struct netdev *netdev,
const struct netdev_tnl_build_header_params *params)
{
const struct netdev_tunnel_config *tnl_cfg;
+ union ovs_16aligned_in6_addr *s;
const struct in6_addr *segs;
struct srv6_base_hdr *srh;
- struct in6_addr *s;
ovs_be16 dl_type;
int nr_segs;
int i;
@@ -978,8 +978,7 @@ netdev_srv6_build_header(const struct netdev *netdev,
return EOPNOTSUPP;
}
- s = ALIGNED_CAST(struct in6_addr *,
- (char *) srh + sizeof *srh);
+ s = (union ovs_16aligned_in6_addr *) (srh + 1);
for (i = 0; i < nr_segs; i++) {
/* Segment list is written to the header in reverse order. */
memcpy(s, &segs[nr_segs - i - 1], sizeof *s);
diff --git a/lib/odp-util.c b/lib/odp-util.c
index 21f34d955..724e6f2bc 100644
--- a/lib/odp-util.c
+++ b/lib/odp-util.c
@@ -1820,8 +1820,8 @@ ovs_parse_tnl_push(const char *s, struct
ovs_action_push_tnl *data)
} else if (ovs_scan_len(s, &n, "srv6(segments_left=%"SCNu8,
&segments_left)) {
struct srv6_base_hdr *srh = (struct srv6_base_hdr *) (ip6 + 1);
+ union ovs_16aligned_in6_addr *segs;
char seg_s[IPV6_SCAN_LEN + 1];
- struct in6_addr *segs;
struct in6_addr seg;
uint8_t n_segs = 0;
@@ -1844,7 +1844,7 @@ ovs_parse_tnl_push(const char *s, struct
ovs_action_push_tnl *data)
return -EINVAL;
}
- segs = ALIGNED_CAST(struct in6_addr *, srh + 1);
+ segs = (union ovs_16aligned_in6_addr *) (srh + 1);
segs += segments_left;
while (ovs_scan_len(s, &n, IPV6_SCAN_FMT, seg_s)
--
2.45.0
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