Re: uid_t and gid_t vs. __kernel_uid_t and __kernel_gid_t

[Ralf Baechle]

On Mon, May 14, 2001 at 09:14:26PM +0000, Petr Vandrovec wrote:

> > I had to communicate uid/gid from an application down 
> > to a driver, and discovered that uid and gid in user
> > space are different from those in kernel space.
> 
> ncpfs uses 'unsigned long' in its ncp_mount_data_v4, as MIPS uses
> 'long' type for uid/gid. Unfortunately it still needs conversions
> on some archs, so maybe using u_int64_t is just best solution
> (AFAIK as MIPS unsigned long is 64bit, you have to use u_int64_t
> if you want same type accross architectures).

Only for the 64 bit ABI and kernel on MIPS have a long data type of 64 bits.
General rule for Linux sizeof(pointer) = sizeof(long).

> Kernel part then just checks wheter uid == (__kernel_uid_t)uid and 
> gives up if they differ.

Otherwise funny ones line (u16) 65536 == 0 -> root access could happen ...

  Ralf