Re: [PATCH] swapon: check validity of swap_flags

[Hugh Dickins]

On Fri, 23 Mar 2012, Andrew Morton wrote:
> On Fri, 23 Mar 2012 13:48:35 -0700 (PDT)
> Hugh Dickins <hughd@xxxxxxxxxx> wrote:
> 
> > Most system calls taking flags first check that the flags passed in are
> > valid, and that helps userspace to detect when new flags are supported.
> > 
> > But swapon never did so: start checking now, to help if we ever want to
> > support more swap_flags in future.
> > 
> > It's difficult to get stray bits set in an int, and swapon is not widely
> > used, so this is most unlikely to break any userspace; but we can just
> > revert if it turns out to do so.
> 
> It would be safer to emit a nasty message then let the swapon proceed
> as before.

Safer, I suppose, but I really don't expect that case to arise (we'll
have been doing those lovely runtime discards without asking for a year
now if so).  And it does spoil the checking of supported flags.

Hugh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/