__sctp_rcv_asconf_lookup() in net/sctp/input.c only checks that the ASCONF
chunk can hold the ADDIP header and a parameter header, then calls
af->from_addr_param(), which reads the full address (16 bytes for IPv6)
trusting the parameter's declared length.
An unauthenticated peer can send a truncated trailing ASCONF chunk that
declares an IPv6 address parameter but stops after the 4-byte parameter
header; reached from the no-association lookup path, from_addr_param() then
reads uninitialized bytes past the parameter.
Impact: an unauthenticated SCTP peer makes the receive path read up to 16
bytes of uninitialized memory past a truncated ASCONF address parameter.
The sibling __sctp_rcv_init_lookup() bounds parameters with
sctp_walk_params(); this path open-codes the fetch and omits the bound.
Verify the whole address parameter lies within the chunk before
from_addr_param() reads it, the same class of fix as commit 51e5ad549c
("net: sctp: fix KMSAN uninit-value in sctp_inq_pop").
Fixes: df21857714 ("[SCTP]: Update association lookup to look at ASCONF chunks as well")
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20260608122234.459098-1-michael.bommarito@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
f8373d7090