[dpdk-dev] [PATCH] net/failsafe: fix exec parameter parsing error flow

Gaëtan Rivet gaetan.rivet at 6wind.com
Tue Aug 29 18:33:39 CEST 2017


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.

> 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.

> Fixes: a0194d828100 ("net/failsafe: add flexible device definition")
> Fixes: 35ffe4208140 ("net/failsafe: fix missing pclose after popen")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Matan Azrad <matan at 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;
>  		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


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