Re: [RFC] correct flags to f_mode conversion in __dentry_open

From: Alan Cox
Date: Sat Mar 15 2008 - 18:00:46 EST


On Wed, Mar 12, 2008 at 02:25:27PM -0400, Eric Paris wrote:
> I recently tried to add an SELinux BUG_ON in the case where the kernel
> made a permission request for no permissions and was able to stumble
> over it with something as simple as
>
> open("/dev/null", 3);
>
> Notice that 3 == (O_RDWR | O_WRONLY)
>
> First question, is 3 ever a valid flag from from userspace to sys_open?

Yes.

> does 11 really mean and should it really always be mapped to (FMODE_READ
> | FMODE_WRITE) or should it continue to get mapped to 'no permission?'

We've always mapped 3 to "no permission" to read or write. It's a linuxism


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