Re: [PATCH 1/2] kernel/sys.c: return the current gid when erroroccurs

From: Oleg Nesterov
Date: Wed Aug 07 2013 - 12:27:26 EST

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().

And perhaps the man page should be changed. Add Michael.


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