Re: [PATCH] init: Add strictinit to disable init= fallbacks

[Randy Dunlap <rdunlap@infradead.org>]

On 09/25/14 17:55, Andy Lutomirski wrote:
> If a user puts init=/whatever on the command line and /whatever
> can't be run, then the kernel will try a few default options before
> giving up.  If init=/whatever came from a bootloader prompt, then
> this probably makes sense.  On the other hand, if it comes from a
> script (e.g. a tool like virtme or perhaps a future kselftest
> script), then the fallbacks are likely to exist, but they'll do the
> wrong thing.  For example, they might unexpectedly invoke systemd.
> 
> This adds a new option called strictinit.  If init= and strictinit
> are both set, and the init= binary is not executable, then the
> kernel will panic immediately.  If strictinit is set but init= is
> not set, then strictinit will have no effect, because the only real
> alternative would be to panic regardless of the contents of the root
> fs.
> 
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
>  Documentation/kernel-parameters.txt |  8 ++++++++
>  init/main.c                         | 10 ++++++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 10d51c2f10d7..60f8b3a7a506 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3236,6 +3236,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  	stifb=		[HW]
>  			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
>  
> +	strictinit	[KNL,BOOT]
> +			Normally, the kernel can't find the init binary

			        , if the kernel

> +			specified by rdinit= and/or init=, then it will
> +			try several fallbacks.  If strictinit is set
> +			and the value specified by init= does not work,
> +			then the kernel will panic instead.
> +			This has no effect if init= is not specified.
> +
>  	sunrpc.min_resvport=
>  	sunrpc.max_resvport=
>  			[NFS,SUNRPC]


-- 
~Randy