In the Linux kernel, the following vulnerability has been resolved:

tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()

In some cases, iptunnel_pmtud_check_icmp() can be called while
skb transport header is not set.

This triggers an out-of-bound access, because
(typeof(skb->transport_header))~0U is 65535.

Access the icmp header based on IPv4 network header,
after making sure icmp->type is present in skb linear part.

Note that iptunnel_pmtud_check_icmpv6()) is fine.

https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93

https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d

https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c

https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4

https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7

https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e

https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c

https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec

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