Re: [PATCH v5] fs: clear file privilege bits when mmap writing

[Willy Tarreau <w@1wt.eu>]

On Thu, Dec 10, 2015 at 08:06:35AM +0100, Willy Tarreau wrote:
> Hi Kees,
> 
> Why not add a new file flag instead ?
> 
> Something like this (editing your patch by hand to illustrate) :
(...)
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3aa514254161..409bd7047e7e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -913,3 +913,4 @@
>  #define FL_OFDLCK       1024    /* lock is "owned" by struct file */
>  #define FL_LAYOUT       2048    /* outstanding pNFS layout */
> +#define FL_DROP_PRIVS   4096    /* lest something weird decides that 2 is OK */

Crap, these ones are for locks, we need to use O_* instead
But anyway you get the idea, I mean there are probably many spare bits
overthere.

Another option I was thinking about was to change f_mode and detect the
change on close. But I don't know what to compare it against.

Willy

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