Re: [PATCH net] sctp: fix addip_serial increment on ASCONF_ACK allocation failure

On Tue, Jul 28, 2026 at 9:24 PM Jakub Kicinski [off-list ref] wrote:

On Thu, 23 Jul 2026 15:18:18 +0800 luoqing wrote:

quoted

From: Qing Luo <redacted>

In sctp_process_asconf(), when sctp_make_asconf_ack() fails to allocate
the ASCONF_ACK chunk due to memory pressure, the code jumps to the
done label where asoc->peer.addip_serial is unconditionally incremented.

This leaves the peer's ASCONF (serial N) unacknowledged while the local
endpoint now expects serial N+1. When the peer retransmits serial N, it
falls into the serial < addip_serial + 1 branch ,
which attempts to look up a cached ACK for serial N. No cached ACK
exists since the allocation failed, so the retransmission is silently
discarded. The peer eventually times out and ABORTs the association.

Move the addip_serial increment inside the if (asconf_ack) block so that
the serial number is only advanced when the ASCONF_ACK is successfully
created and cached. This way, on allocation failure, the serial number
is unchanged and the peer's retransmitted ASCONF will be correctly
re-processed.

Fixes: 1da177e4c3f4 (Linux-2.6.12-rc2)

nit: missing quotation marks around the subject
--
pw-bot: cr

Somehow I missed this patch.

LGTM, except the nit Jakub pointed out.

Thanks.