netdev - Re: [RFC net-next v2 1/1] net: sched: prevent duplicate flower rules from tcf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 1 Nov 2019 13:01:06 +0000
From:   Vlad Buslov <vladbu@...lanox.com>
To:     John Hurley <john.hurley@...ronome.com>
CC:     Vlad Buslov <vladbu@...lanox.com>, Jiri Pirko <jiri@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "simon.horman@...ronome.com" <simon.horman@...ronome.com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>,
        "louis.peens@...ronome.com" <louis.peens@...ronome.com>,
        "oss-drivers@...ronome.com" <oss-drivers@...ronome.com>
Subject: Re: [RFC net-next v2 1/1] net: sched: prevent duplicate flower rules
 from tcf_proto destroy race


On Thu 31 Oct 2019 at 21:08, John Hurley <john.hurley@...ronome.com> wrote:
> When a new filter is added to cls_api, the function
> tcf_chain_tp_insert_unique() looks up the protocol/priority/chain to
> determine if the tcf_proto is duplicated in the chain's hashtable. It then
> creates a new entry or continues with an existing one. In cls_flower, this
> allows the function fl_ht_insert_unque to determine if a filter is a
> duplicate and reject appropriately, meaning that the duplicate will not be
> passed to drivers via the offload hooks. However, when a tcf_proto is
> destroyed it is removed from its chain before a hardware remove hook is
> hit. This can lead to a race whereby the driver has not received the
> remove message but duplicate flows can be accepted. This, in turn, can
> lead to the offload driver receiving incorrect duplicate flows and out of
> order add/delete messages.
>
> Prevent duplicates by utilising an approach suggested by Vlad Buslov. A
> hash table per block stores each unique chain/protocol/prio being
> destroyed. This entry is only removed when the full destroy (and hardware
> offload) has completed. If a new flow is being added with the same
> identiers as a tc_proto being detroyed, then the add request is replayed
> until the destroy is complete.
>
> v1->v2:
> - put tcf_proto into block->proto_destroy_ht rather than creating new key
>   (Vlad Buslov)
> - add error log for cases when hash entry fails. Previously it failed
>   silently with no indication. (Vlad Buslov)
>
> Fixes: 8b64678e0af8 ("net: sched: refactor tp insert/delete for concurrent execution")
> Signed-off-by: John Hurley <john.hurley@...ronome.com>
> Reviewed-by: Simon Horman <simon.horman@...ronome.com>
> Reported-by: Louis Peens <louis.peens@...ronome.com>
> ---

Hi John,

Patch looks good! However, I think we can simplify it even more and
remove duplication of data in tcf_proto (hashtable key contains copy of
data that is already available in the struct itself) and remove all
dynamic memory allocations. I have refactored your patch accordingly
(attached). WDYT?

[...]


View attachment "ht_refactor1" of type "text/plain" (6325 bytes)