CVE-2023-53333

/// Technical description

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

netfilter: conntrack: dccp: copy entire header to stack buffer, not just basic one

Eric Dumazet says:

nf_conntrack_dccp_packet() has an unique:

dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &_dh);

And nothing more is 'pulled' from the packet, depending on the content.

dh->dccph_doff, and/or dh->dccph_x ...)

So dccp_ack_seq() is happily reading stuff past the _dh buffer.

BUG: KASAN: stack-out-of-bounds in nf_conntrack_dccp_packet+0x1134/0x11c0

Read of size 4 at addr ffff000128f66e0c by task syz-executor.2/29371

[..]

Fix this by increasing the stack buffer to also include room for

the extra sequence numbers and all the known dccp packet type headers,

then pull again after the initial validation of the basic header.

While at it, mark packets invalid that lack 48bit sequence bit but

where RFC says the type MUST use them.

Compile tested only.

v2: first skb_header_pointer() now needs to adjust the siz

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References