Messages in this thread | | | Date | Thu, 08 Aug 2013 09:48:06 +0800 | From | Chen Gang <> | Subject | Re: [PATCH 1/2] kernel/sys.c: return the current gid when error occurs |
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On 08/08/2013 09:35 AM, Andy Lutomirski wrote: > On Wed, Aug 7, 2013 at 6:30 PM, Chen Gang <gang.chen@asianux.com> wrote: >> On 08/08/2013 12:58 AM, Andy Lutomirski wrote: >>> On Wed, Aug 7, 2013 at 9:21 AM, Oleg Nesterov <oleg@redhat.com> wrote: >>>> On 08/06, Andy Lutomirski wrote: >>>>> >>>>> I assume that what the man page means is that the return value is >>>>> whatever fsgid was prior to the call. On error, fsgid isn't changed, so >>>>> the return value is still "current". >>>> >>>> Probably... Still >>>> >>>> On success, the previous value of fsuid is returned. >>>> On error, the current value of fsuid is returned. >>>> >>>> looks confusing. sys_setfsuid() always returns the old value. >>>> >>>>> (FWIW, this behavior is awful and is probably the cause of a security >>>>> bug or three, since success and failure are indistinguishable. >>>> >>>> At least this all looks strange. >>>> >>>> I dunno if we can change this old behaviour. I won't be surprized >>>> if someone already uses setfsuid(-1) as getfsuid(). >>> >> >> Oh, really it is. >> >> Hmm... as a pair function, we need add getfsuid() too, if we do not add >> it, it will make negative effect with setfsuid(). >> >> Since it is a system call, we have to keep compitable. >> >> So in my opinion, better add getfsuid2()/setfsuid2() instead of current >> setfsuid() > > How about getfsuid() and setfsuid2()? >
Hmm... I have 2 reasons, please check.
1st reason: I checked history (just like Kees Cook suggested), getfsuid() is mentioned before (you can google to find it), so need use getfsuid2() to bypass the history complex.
And 2nd reason: getfsuid() seems more like the pair of setfsuid(), not for setfsuid2().
> --Andy > >
Thanks. -- Chen Gang
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