On Wed, 14 Feb 2024 09:56:26 +0100
Laurent Vivier <lvivier(a)redhat.com> wrote:
...
/**
* udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged
@@ -579,6 +562,9 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start,
unsigned n,
*
* Return: size of tap frame with headers
*/
+#pragma GCC diagnostic push
+/* ignore unaligned pointer value warning for &b->iph */
+#pragma GCC diagnostic ignored "-Waddress-of-packed-member"
static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
const struct timespec *now)
{
@@ -614,13 +600,14 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t
dstport,
b->iph.saddr = b->s_in.sin_addr.s_addr;
}
- udp_update_check4(b);
+ b->iph.check = csum_ip4_header(&b->iph);
Similar comment as I had on
v1: I don't think this is safe.
If &b->iph is, say, 0x2000, it's all fine: when csum_ip4_header() needs
to access, say, ip4h->tot_len, it will dereference 0x2000 and look at
16 bits, 2 bytes into it.
If &b->iph is 0x2001, though, csum_ip4_header() will dereference 0x2001
and, on some architectures, boom.