Re: [PATCH v2] sctp: Fix sk_ack_backlog wrap-around problem

From: Daniel Borkmann
Date: Thu Jun 12 2014 - 04:06:37 EST


On 06/12/2014 04:53 AM, Xufeng Zhang wrote:
Consider the scenario:
For a TCP-style socket, while processing the COOKIE_ECHO chunk in
sctp_sf_do_5_1D_ce(), after it has passed a series of sanity check,
a new association would be created in sctp_unpack_cookie(), but afterwards,
some processing maybe failed, and sctp_association_free() will be called to
free the previously allocated association, in sctp_association_free(),
sk_ack_backlog value is decremented for this socket, since the initial
value for sk_ack_backlog is 0, after the decrement, it will be 65535,
a wrap-around problem happens, and if we want to establish new associations
afterward in the same socket, ABORT would be triggered since sctp deem the
accept queue as full.
Fix this issue by only decrementing sk_ack_backlog for associations in
the endpoint's list.

Fix-suggested-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: Xufeng Zhang <xufeng.zhang@xxxxxxxxxxxxx>

Looks good to me, thanks. This also needs to go to -stable.

Acked-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
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