From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stefano Brivio <sbrivio@redhat.com>
To: passt-dev@passt.top
Subject:
 [PATCH] udp: Ignore bogus -Wstringop-overread for write() from gcc 12.1
Date: Thu, 19 May 2022 13:32:46 +0200
Message-ID: <20220519113246.1914500-1-sbrivio@redhat.com>
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With current OpenSUSE Tumbleweed on aarch64 (gcc-12-1.3.aarch64) and
on x86_64 (gcc-12-1.4.x86_64), but curiously not on armv7hl
(gcc-12-1.3.armv7hl), gcc warns about using the _pointer_ to the
802.3 header to write the whole frame to the tap descriptor:
  reading between 62 and 4294967357 bytes from a region of size 14

which is bogus:
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103483

Probably declaring udp_sock_fill_data_v{4,6}() as noinline would
"fix" this, but that's on the data path, so I'd rather not. Use
a gcc pragma instead.

Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
 udp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/udp.c b/udp.c
index f425d14..dd7119e 100644
--- a/udp.c
+++ b/udp.c
@@ -714,8 +714,10 @@ static void udp_sock_fill_data_v4(const struct ctx *c, i=
nt n,
 	b->uh.len =3D htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
=20
 	if (c->mode =3D=3D MODE_PASTA) {
+#pragma GCC diagnostic ignored "-Wstringop-overread"
 		if (write(c->fd_tap, &b->eh, sizeof(b->eh) + ip_len) < 0)
 			debug("tap write: %s", strerror(errno));
+#pragma GCC diagnostic pop
 		pcap((char *)&b->eh, sizeof(b->eh) + ip_len);
=20
 		return;
@@ -813,8 +815,10 @@ static void udp_sock_fill_data_v6(const struct ctx *c, i=
nt n,
 	b->ip6h.hop_limit =3D 255;
=20
 	if (c->mode =3D=3D MODE_PASTA) {
+#pragma GCC diagnostic ignored "-Wstringop-overread"
 		if (write(c->fd_tap, &b->eh, sizeof(b->eh) + ip_len) < 0)
 			debug("tap write: %s", strerror(errno));
+#pragma GCC diagnostic pop
 		pcap((char *)&b->eh, sizeof(b->eh) + ip_len);
=20
 		return;
--=20
2.35.1


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