ipaccess-proxy: reject oversized IPA frame length

ipaccess_proxy_read_msg() reads the 16-bit IPA frame length from the
wire header and passes it straight as the recv() count into a msgb that
was allocated with a fixed PROXY_ALLOC_SIZE (1200) bytes, without ever
checking it against the buffer tailroom. A peer that advertises a body
length larger than the remaining buffer space makes recv() write past
the end of the heap allocation (heap buffer overflow).

Reject frames whose advertised length exceeds the msgb tailroom, the
same way the other IPA read paths bound the read to msgb_tailroom().

Also reject a short (split) IPA header: recv() of the 3-byte header can
return fewer than 3 bytes on a stream socket, which left msg->l2h ahead
of msg->tail while the length was validated against msgb_tailroom()
(measured from msg->tail), so a 1-2 byte body overflow was still
possible. Bail out on a short header, as the other IPA read paths do.

This issue has been assigned the CVE candidate identifier
CAN-2026-2051036.

Change-Id: I05137e114eaa99ff0e85eecccf7645c90945214f
---
M src/ipaccess/ipaccess-proxy.c
1 file changed, 16 insertions(+), 0 deletions(-)