On Tue, 2015-09-29 at 18:07 +0100, Ian Jackson wrote:
> Stefano Stabellini writes ("Re: [PATCH v7] run QEMU as non-root"):
> > On Fri, 7 Aug 2015, Wei Liu wrote:
> > > Please use for / while to loop.
> >
> > The goto retry loop is a very common patter for error handling, but I
> > can turn it into a loop if you are keen on it.
>
> I'm afraid I agree with Wei here.
>
> > > Also you might want to save and restore errno.
> >
> > Across the getpwnam_r call? Or across the loop? Or across the function
> > libxl__dm_runas_helper?
>
> I don't understand either. Also I don't understand why you set errno
> to 0.
getpwnam(7) says:
RETURN VALUE
The getpwnam() and getpwuid() functions return a pointer to a
passwd structure, or NULL if the matching entry is not found
or an error occurs. If an error occurs, errno is set appro‐
priately. If one wants to check errno after the call, it
should be set to zero before the call.
But this code is using the _r variants, on which the manpage later says:
On success, getpwnam_r() and getpwuid_r() return zero, and
set *result to pwd. If no matching password record was
found, these functions return 0 and store NULL in *result.
In case of error, an error number is returned, and NULL is
stored in *result.
So I guess the errno is either a leftover from not using _r in an earlier
version or from applying the first para above to the wrong functions.
Ian.
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