virtio-net: Ensure that TCP packets don't overflow gso_segs

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The user can specify any gso_size in a packet crafted with an AF_PACKET
PACKET_VNET_HDR socket, even smaller than TCP_MIN_GSO_SIZE = 8. At the
same time, GSO_MAX_SIZE = 8 * GSO_MAX_SEGS = 8 * 65535. When the user
crafts a packet with gso_size < 8, there is a risk for partial GSO to
overflow the 16-bit gso_segs field when dividing the SKB length by
gso_size.

Adjust gso_size of TCP packets to be at least TCP_MIN_GSO_SIZE = 8. Keep
gso_size of UDP GSO packets, as gso_size=1 is valid and explicitly
tested at tools/testing/selftests/net/tun.c:649.

Fixes: 7c6d2ecbda ("net: be more gentle about silly gso requests coming from user")
Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260822120117.1163423-2-alice.kernel@fastmail.im
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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Alice Mikityanska 2026-08-22 15:01:16 +03:00 • committed by Paolo Abeni

parent 2c4e7c42d7

commit c27c449d45

1 changed files with 4 additions and 0 deletions

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include/linux/virtio_net.h

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