Re: [PATCH][linux-next] net/smc: prevent NULL dereference in smc_find_rdma_v2_device_serv()

[Tim Gardner]

On 10/19/21 12:33 AM, Karsten Graul wrote:
> On 18/10/2021 20:31, Tim Gardner wrote:
> > Coverity complains of a possible NULL dereference in smc_find_rdma_v2_device_serv().
> >
> > 1782        smc_v2_ext = smc_get_clc_v2_ext(pclc);
> > CID 121151 (#1 of 1): Dereference null return value (NULL_RETURNS)
> > 5. dereference: Dereferencing a pointer that might be NULL smc_v2_ext when calling smc_clc_match_eid. [show details]
> > 1783        if (!smc_clc_match_eid(ini->negotiated_eid, smc_v2_ext, NULL, NULL))
> > 1784                goto not_found;
> >
> > Fix this by checking for NULL.
>
> Hmm that's a fundamental question for me: do we want to make the code checkers happy?
> While I understand that those warnings give an uneasy feeling I am not sure
> if the code should have additional (unneeded) checks only to avoid them.

Coverity produces a lot of false positives. I thought this one might be 
legitimate, but if you're comfortable that its not an issue then I'm OK 
with that.

> In this case all NULL checks are initially done in smc_listen_v2_check(),
> afterwards no more NULL checks are needed. When we would like to add them
> then a lot more checks are needed, e.g. 3 times in smc_find_ism_v2_device_serv()
> (not sure why coverity does not complain about them, too).
>
> Thoughts?

Coverity probably has produced a report from the other call sites if 
you've used a similar pattern, I just hadn't gotten to them yet.

I'll just mark them all as false positives.

rtg
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Tim Gardner
Canonical, Inc