Re: [PATCH] net/failsafe: fix exec parameter parsing error flow

[Matan Azrad <matan@mellanox.com>]

Hi Gaetan

> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> Sent: Tuesday, August 29, 2017 7:34 PM
> To: Matan Azrad <matan@mellanox.com>
> Cc: dev@dpdk.org; Raslan Darawsheh <rasland@mellanox.com>;
> stable@dpdk.org
> Subject: Re: [PATCH] net/failsafe: fix exec parameter parsing error flow
> 
> Hi Matan,
> 
> On Tue, Aug 29, 2017 at 05:59:08PM +0300, Matan Azrad wrote:
> > The corrupted code returns success value in case of the execution
> > process output stream is empty(EOF).
> > It causes to segmentation fault while failsafe polls this command line
> > again, than gets success and tries to do hotplug add to the sub device
> > by uninitialized pointer dereferencing.
> >
> 
> This is a bug and should be fixed, thanks.
> 
> > Morever, when the output is not empty but uncorrect, failsafe returns
> > error for its probe function while the expected behavior is to do
> > polling until the output is correct.
> >
> 
> The expected behavior is for the fail-safe to return an error if the execution
> of the given command returns an error.
> 
> The intention is that users writing such script would be able to output a blank
> lines in case there is nothing to probe, but still remain aware of issues during
> the execution of the command.
> 
> The fail-safe ignores errors pertaining to absent devices due to its nature.
> This does not mean that it should ignore all errors and try to keep on going
> while everything else is on fire.
> 
> The contract with the user is that "blank line" without other errors means
> "absent device". Garbled output or return code != 0 means runtime error
> and should be thrown to the user / application.
> 

OK, good, I would have signed this contract :)

What's about if the parsing is not empty and out with error in the polling process?
I think in current code failsafe just continues normally and tries again on next polling time.
Because of this code I thought that if error occurs we should poll it again...

Can you please add it (the contract) in failsafe documentation for exec parameter?

> > The fix changes the return value to be -ENODEV for this sub device in
> > the two cases.
> > By this way, failsafe tries to parse this sub device parameter by exec
> > method until the output is correct.
> >
> 
> The issue is that this portion of the code will be heavily modified anyway. The
> errno handling is erroneous and must be fixed, which is in conflict with your
> patch.
> 
> I will send the intended fix shortly, referencing this patch and the issue your
> highlighted, but both patch won't be compatible.
> 

Good, no problems.

> > Fixes: a0194d828100 ("net/failsafe: add flexible device definition")
> > Fixes: 35ffe4208140 ("net/failsafe: fix missing pclose after popen")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Matan Azrad <matan@mellanox.com>
> > ---
> >  drivers/net/failsafe/failsafe_args.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/failsafe/failsafe_args.c
> > b/drivers/net/failsafe/failsafe_args.c
> > index 645c885..61c55df 100644
> > --- a/drivers/net/failsafe/failsafe_args.c
> > +++ b/drivers/net/failsafe/failsafe_args.c
> > @@ -157,12 +157,16 @@ fs_execute_cmd(struct sub_device *sdev, char
> *cmdline)
> >  	ret = fs_parse_device(sdev, output);
> >  	if (ret) {
> >  		ERROR("Parsing device '%s' failed", output);
> > +		ret = -ENODEV;

Remove the above line for probe function error report.

> >  		goto ret_pclose;
> >  	}
> >  ret_pclose:
> >  	pclose_ret = pclose(fp);
> >  	if (pclose_ret) {
> > -		pclose_ret = errno;
> > +		if (errno == 0)
> > +			errno = -(pclose_ret = ret);
> > +		else
> > +			pclose_ret = errno;
> >  		ERROR("pclose: %s", strerror(errno));
> >  		errno = old_err;
> >  		return pclose_ret;
> > --
> > 2.7.4
> >
> 
> Best regards,
> --
> Gaëtan Rivet
> 6WIND

Thanks,
Matan Azrad