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Message-ID: <ZMDNjD46BvZ5zp5I@corigine.com>
Date: Wed, 26 Jul 2023 09:38:52 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Ratheesh Kannoth <rkannoth@...vell.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, Sunil Kovvuri Goutham <sgoutham@...vell.com>
Subject: Re: [PATCH net-next] flow_dissector: Add IPSEC dissectors
On Wed, Jul 26, 2023 at 06:34:34AM +0000, Ratheesh Kannoth wrote:
> > From: Simon Horman <simon.horman@...igine.com>
> > Sent: Wednesday, July 26, 2023 1:21 AM
> > Subject: [EXT] Re: [PATCH net-next] flow_dissector: Add IPSEC dissectors
>
>
> > > FLOW_DISSECTOR_KEY_NUM_OF_VLANS, /* struct
> > flow_dissector_key_num_of_vlans */
> > > FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe
> > */
> > > FLOW_DISSECTOR_KEY_L2TPV3, /* struct flow_dissector_key_l2tpv3
> > */
> > > + FLOW_DISSECTOR_KEY_IPSEC, /* struct flow_dissector_key_ipsec */
> > > FLOW_DISSECTOR_KEY_CFM, /* struct flow_dissector_key_cfm */
> > >
> > > FLOW_DISSECTOR_KEY_MAX,
> >
> > ...
> >
> > Hi Ratheesh,
> >
> > With this change, this enum now has 33 values, excluding
> > FLOW_DISSECTOR_KEY_MAX. I.e the range of values is from 0 to 32.
> >
> > But dissector_uses_key() looks like this:
> >
> >
> > static inline bool dissector_uses_key(const struct flow_dissector
> > *flow_dissector,
> > enum flow_dissector_key_id key_id) {
> > return flow_dissector->used_keys & (1 << key_id); }
> >
> > And the type of the used_keys field of struct flow_dissector is unsigned int, a
> > 32bit entity.
> >
> > So an overflow will now occur if key_id is FLOW_DISSECTOR_KEY_CFM.
> >
> > This is flagged by Sparse.
> >
Hi Ratheesh,
> Thank you !
> 1) How did you run sparse to detect this error. When I ran below command, it did not throw this error/warning ?
> make C=2 net/core/ V=s
I ran:
make C=2 net/core/flow_dissector.o
FWIIW, I also saw the warning using make C=2 net/core/ V=s
> sparse version is 0.6.4
I am using sparse git commit ce1a6720f69e, because at one point that
was the newest revision at a time the packaged version I had wasn't working
for me, and that was the latest commit at the time.
https://git.kernel.org/pub/scm/devel/sparse/sparse.git/commit/ce1a6720f69e
> 2) Is it okay to change variable type of "used_keys" from "unsigned int" to "unsigned long long" to accommodate this.
> This variable is used at lot of places in the code.
I might go for u64.
But yes, I suspect making the variable wider is a viable solution.
Given that it is widely used it would be good to inspect
how it is used to make sure this change makes sense.
I would make this change a separate patch if it is more than one line.
Also, while you are there, can you fix the spelling mistake in
the comment on the 'used_keys' line in struct flow_dissector ?
It's the same line that needs to be changed to change the type of 'used_keys'.
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